opinion: Justice Rehnquist
  delivered the opinion of the Court.
  Last Term in Schweiker v. Gray Panthers, 453 U. S. 34, 49-50 (1981), we upheld the validity of federal Medicaid regulations that permit “deeming” of income between spouses in those States that have exercised the so-called “§ 209(b) option” provided for in the Social Security Act, 79 Stat. 343, as amended, 42 U. S. C. § 1396 et seq. (1976 ed. and Supp. III). “Deeming,” in the parlance of the Social Security laws and regulations, means that a State determines eligibility by assuming that a portion of the spouse’s income is “available” to the applicant. Because an individual’s eligibility for Medicaid benefits depends in part on the financial resources that are “available” to him, “[djeeming. . . has the effect of reducing both the number of eligible individuals and the amount of assistance paid to those who qualify.” Schweiker v. Gray Panthers, supra, at 36. We rejected contentions that these regulations were arbitrary or capricious and that the regulations were inconsistent with § 1902(a)(17) of the Social Security Act, 42 U. S. C. § 1396a(a)(17). 453 U. S., at 43. In the present case, we are called upon to decide to what extent the State of Iowa, an “SSI State,” may consider the income of the institutionalized Medicaid applicant’s noninstitutionalized spouse in determining eligibility for Medicaid.
  As we explained in greater detail in Gray Panthers, supra, Medicaid as originally enacted “required participating States to provide medical assistance to ‘categorically needy’ individuals who received cash payments under one of four welfare programs established elsewhere in the [Social Security] Act.” Id., at 37. This program was restructured in 1972 by Congress, when it replaced three of the four categorical programs with Supplemental Security Income for the Aged, Blind, and Disabled (SSI), 42 U. S. C. § 1381 et seq. (1976 ed. and Supp. III). Fearing that some States might withdraw from the Medicaid program rather than bear the increased costs imposed by the restructuring, Congress offered the States the “§ 209(b) option.” 42 U. S. C. § 1396a(f). Under the § 209(b) option, the States may elect to provide Medicaid assistance only to those individuals who would have been eligible under the State’s Medicaid plan in effect on January 1, 1972. In other words, the § 209(b) option allows the States to avoid the effect of the link between the SSI and Medicaid programs: States may become either “§ 209(b) States” or “SSI States.”
  If a State participates in the Medicaid program without exercising the § 209(b) option, the State is required to make Medicaid assistance available to all recipients of SSI benefits. 42 U. S. C. § 1396a(a)(10)(A); 42 CFR §435.120 (1980). SSI States, however, are not limited to providing Medicaid benefits to SSI recipients. The Medicaid program offers participating States the option of providing Medicaid assist-anee to certain other groups of individuals, see 42 U. S. C. § 1396a(a)(10)(C), one of which is the “optional categorically needy.” See 42 CFR §§435.200-435.231 (1980). Included among the “optional categorically needy,” are (1) individuals who would be eligible for, but for some reason are not receiving, SSI benefits and (2) individuals who would be eligible for SSI benefits but for their institutionalized status. 42 CFR §§435.210-435.211 (1980).
  With regard to the “optional categorically needy,” the Secretary’s regulations require the States to “deem” the income and resources of spouses who share the same household. 42 CFR §435.723(b) (1980). Where both spouses are eligible for Medicaid, the States must “deem” income for the first six months after the spouses cease to live together. After this 6-month period, the States may consider only the income and resources actually contributed by one spouse to the other. § 435.723(c). If only one spouse is eligible for Medicaid, a similar rule applies but the time period is one month instead of six. § 435.723(d). In effect, § 435.723 places time limitations on the States’ ability to consider the spouse’s income as “available” to the applicant after the spouses cease to live together. The question addressed by the lower courts, and now presented for our decision, is whether this regulation is a permissible exercise of the Secretary’s authority under the Act to define what income is “available.”
  I
  Petitioner Elvina Herweg has been in a comatose state since August 1976 as a result of two cerebral hemorrhages. When she was placed in a long-term care facility, her husband, petitioner Darrell Herweg, applied for Medicaid assistance on Elvina’s behalf. Elvina does not receive SSI benefits, although .the parties and the United States as amicus curiae agree that she is eligible to receive such benefits. Iowa applied its own formula to determine Elvina’s eligibility for Medicaid and to ascertain the amount Darrell would be required to contribute toward his wife’s care. This formula was based on the income Darrell earned as a butcher and on standard living allowances allowed Darrell and his three children living at home. In other words, Iowa was “deeming,” or attributing, income earned by one spouse to the other.
  Iowa, however, was deeming in a manner inconsistent with the Secretary’s regulations, which place time limitations upon the States’ ability to consider as available to the applicant his spouse’s income where the spouses do not share the same household. Swpra, at 269 and this page, and n. 4. Because Elvina was institutionalized and because Darrell is not eligible for Medicaid, the Secretary’s regulations prohibit Iowa from considering Darrell’s income after one month from the time the couple ceased to live together. See 42 CFR § 435.723(d) (1980).
  Petitioners filed the instant suit in the United States District Court for the Southern District of Iowa challenging Iowa’s “deeming” of the income of a Medicaid applicant’s spouse. After certifying a class of plaintiffs, the District Court held that § 1902(a)(17) of the Social Security Act, 42 U. S. C. § 1396a(a)(17), required Iowa’s procedures to “provide for a factual determination in each instance of the amount of the spouse’s income which is in fact reasonably available for the support of the institutionalized spouse. . . . Such determination must give due consideration to the individual obligations and the particular needs of each spouse and family.” 443 F. Supp. 1315, 1319 (1978). In interpreting § 1902(a)(17), the District Court concluded that “ ‘deeming’ is contrary to congressional intent whether income of the non-institutionalized spouse is deemed available or unavailable.” Id., at 1320. The District Court noted that the predecessor to 42 CFR 435.723 (1980) was inconsistent with its interpretation of § 1902(a)(17). In the District Court’s view, therefore, the Secretary’s regulation was inconsistent with §1902(a)(17) because the regulation disabled the States in certain instances from considering the spouse’s income as available to the applicant.
  In response to this order, Iowa adopted a procedure for making individualized factual determinations of the amount of income available to an institutionalized spouse. The District Court approved this plan and petitioners appealed. The Court of Appeals for the Eighth Circuit affirmed by an equally divided Court. 619 F. 2d 1265 (1980) (en banc). We reverse.
  II
  Although Elvina Herweg does not receive SSI benefits, the class certified without objection by the District Court includes SSI recipients. We therefore construe the order entered by the District Court, and the plan adopted by Iowa in response, as applying both to SSI recipients and to the optional categorically needy.
  A
  With regard to recipients of SSI benefits, the District Court’s order clearly conflicts with § 1902(a)(10)(A) of the Social Security Act, 42 U. S. C. § 1396a(a)(10)(A), which requires States not having exercised the § 209(b) option to provide Medicaid assistance to all SSI recipients. 42 CFR §435.120 (1980). See Beltran v. Myers, 451 U. S. 625, 626, n. 3 (1981). The SSI program, contained in Title XVI of the Social Security Act, 42 U. S. C. § 1382 et seq. (1976 ed. and Supp. Ill), contains its own eligibility provisions. See, e. g., 42 U. S. C. §§ 1382(a)(1), 1382c(b), (f)(1). Pursuant to the District Court’s order, however, Iowa is permitted to deny Medicaid benefits to institutionalized SSI recipients if, after making an individualized factual determination, Iowa concludes that the income of the SSI recipient’s spouse should be considered available even though it was not actually contributed. Because Congress has clearly spoken in this regard, to the extent it permits Iowa to deny Medicaid assistance to SSI recipients, the District Court’s order cannot stand.
  In requiring individualized determinations of income available to the Medicaid applicant, the District Court held that the Secretary has exceeded his authority in permitting any “deeming” whatsoever. In Schweiker v. Gray Panthers, 453 U. S., at 45, however, we held that Congress intended to permit a state Medicaid plan to deem the income from the applicant’s spouse as part of the available income which the state plan may consider in determining eligibility. Thus, to the extent that the District Court’s order forbids deeming under any circumstances, the order conflicts with our decision in Gray Panthers.
  B
  The issue that remains, therefore, is whether § 1902(a)(17) precludes the Secretary from promulgating regulations that impose time limitations upon the States’ ability to consider the income of the institutionalized applicant’s spouse.
  Relying on § 1902(a)(17)(D), respondents argue that the Secretary has exceeded his authority in placing time limitations upon the States’ authority to consider the financial responsibility of spouses. Subsection (17)(D), respondents argue, evidences Congress’ intent to permit the States to consider the financial responsibility of spouses and parents. Nothing in the statute or the legislative history, respondents contend, suggests that Congress intended to prevent the States from enforcing their financial responsibility policies simply because the Medicaid applicant is institutionalized.
  We think, however, that respondents overemphasize the effect of subsection (17)(D). That provision may not be read independently of subsection (17)(B). Subsection (17)(B) provides that participating States must grant benefits to eligible individuals “taking into account only such income and resources as are, as determined in accordance with standards prescribed by the Secretary, available to the applicant.” 42 U. S. C. § 1396a(a)(17)(B) (emphasis added). In Gray Panthers, we recognized that subsection (17)(B) delegates to the Secretary broad authority to prescribe standards setting eligibility requirements for state Medicaid plans. In view of Congress’ explicit delegation of authority to give substance to the meaning of “available,” the Secretary’s definition of the term is “‘entitled to more than mere deference or weight.’” Schweiker v. Gray Panthers, supra, at 44, quoting Batterton v. Francis, 432 U. S. 416, 426 (1977). Because Congress has entrusted the primary responsibility of interpreting a statutory term to the Secretary rather than to the courts, his definition is entitled to “ ‘legislative effect.’ ” Schweiker v. Gray Panthers, supra, at 44; Batterton v. Francis, supra, at 426. As in Gray Panthers and Batterton, our review is limited to determining whether the Secretary has exceeded his statutory authority and whether the regulation is arbitrary and capricious.
  Although Congress has approved of some deeming of income between Medicaid applicants and their spouses, Schweiker v. Gray Panthers, supra, at 48, we cannot agree with respondents that Congress intended the States to enforce their spousal responsibility policies wholly unimpeded by the Secretary’s congressionally authorized power to give substance to the term “available.” In placing time limitations upon the States’ ability to consider the spouse’s income where the Medicaid applicant and his spouse no longer live together, the Secretary has done nothing more than define what income is “available.” Although Congress intended that a spouse’s income could be part of the income which the Secretary may determine should be considered by the States as available to the Medicaid applicant, Schweiker v. Gray Panthers, supra, at 45, we see nothing in subsection (17)(D) that precludes the Secretary from imposing upon the States the time limits at issue in the instant case. We find nothing in subsection (17)(D) either that disables the Secretary from defining the term “available” in such circumstances, or that gives the States authority to “deem” income unimpeded by the Secretary’s authority under subsection (17)(B). Subsection (17)(D) cannot be read to require the Secretary to permit the States to consider the income of a spouse no longer living with the applicant as available to the applicant for an unlimited duration.
  Although we do not agree with the contention of the United States, and apparently that of petitioners, that the time limitations in 42 CFR §435.723 (1980) are compelled by the relationship between the Medicaid and SSI programs, we do agree that the Secretary may acknowledge this relationship in defining “availability” of income with regard to Medicaid applicants within the optional categories. As we have explained, the optional categorically needy consists in part of those individuals who are eligible for, but are not receiving, SSI benefits and those individuals who, but for their institutionalization, would be eligible for SSI benefits. Supra, at 269. Since these groups are defined in part with regard to SSI income limitations, it is reasonable that the Secretary should determine that States electing to provide Medicaid assistance to the optional categorically needy should apply a similar method for calculating income as that employed in the SSI program. The 1-month and 6-month limitations in 42 CFR §435.723 (1980) are virtually identical to the SSI requirements. See 42 U. S. C. §§ 1382(a)(1), 1382c(b), (f)(1). We cannot say that it is either arbitrary or capricious for the Secretary to conclude that SSI recipients and the optional categorically needy should be treated similarly with respect to the method used for calculating income in determining whether the State is entitled to receive federal financial assistance under the Medicaid program.
  In upholding the Secretary’s limitation on deeming, we do not thereby render subsection (17)(D) meaningless. That provision, however, may not be read in isolation from the other provisions of the Social Security Act. We have no doubt that some tension exists between the Secretary’s con-gressionally authorized power under subsection (17)(B) to determine what income is “available” to the applicant and Congress’ intent in subsection (17)(D) to permit the States to enforce their spousal responsibility policies. Because Congress in subsection (17)(B) has delegated broad authority to the Secretary to set eligibility standards for the Medicaid program, however, we cannot say that the Secretary’s regulations placing time limitations on the States’ ability to deem income between spouses who do not share the same household are unreasonable or contrary to law. A reviewing court may not set aside the Secretary’s regulations “simply because it would have interpreted the statute in a different manner.” Batterton v. Francis, supra, at 425. A fortiori, Iowa may not ignore federal regulations simply because it interprets § 1902(a)(17) in a manner it considers preferable to the Secretary’s interpretation.
  This would be a different case, and respondents’ arguments more compelling, if the Secretary had sought to use his authority under subsection (17)(B) to foreclose entirely the States’ ability to consider the income of the institutionalized applicant’s spouse. Such a reading of the statute could well render subsection (17)(D) superfluous. See Schweiker v. Gray Panthers, 453 U. S., at 45. The Secretary’s regulations, however, impose no such across-the-board limitation on the States’ ability to implement their spousal responsibility policies. The challenged regulation applies only to those SSI States that have decided to extend Medicaid benefits to the optional categorically needy, and it prohibits deeming only after the spouses have ceased to live together for prescribed periods of time.
  On the contrary, 42 CFR §435.723 (1980) is simply an exception to the general rule that the spouse’s income may be considered available to the applicant. With regard to the optional categorically needy, SSI States are required to deem the income and resources of spouses living in the same household. § 435.723(b). States exercising the § 209(b) option are required to deem income to the extent required in SSI States and may deem to the full extent they did before 1972. §435.734. See Schweiker v. Gray Panthers, supra, at 40. Finally, the SSI applicant is considered to a similar extent to have available to him his spouse’s income and financial resources. See n. 2, supra.
  We conclude that the Secretary need not interpret § 1902 (a)(17) to require an individualized factual determination in each instance as to the amount of income of an applicant’s spouse that may reasonably be considered available to the applicant. With regard to SSI recipients in SSI States, such an interpretation would be contrary to § 1902(a)(10)(A), 42 U. S. C. § 1396a(a)(10)(A). With regard to the optional categorically needy, we find that the Secretary has not exceeded his authority in promulgating 42 CFR §435.723 (1980), and that this regulation is neither arbitrary nor capricious. Accordingly, we reverse the judgment of the Court of Appeals for the Eight Circuit and remand for proceedings consistent with this opinion.
  It is so ordered.
  Section 1902(a)(17) provides that a state plan for medical assistance must
  "include reasonable standards ... for determining eligibility for and the extent of medical assistance under the plan which (A) are consistent with the objectives of this subchapter, (B) provide for taking into account only such income and resources as are, as determined in accordance with standards prescribed by the Secretary, available to the applicant or recipient . . . (C) provide for reasonable evaluation of any such income or resources, and (D) do not take into account the financial responsibility of any individual for any applicant or recipient under the plan unless such applicant or recipient is such individual’s spouse or such individual’s child who is under age 21 or (with respect to States eligible to participate in the State program established under subchapter XVI of this chapter), is blind or permanently and totally disabled, or is blind or disabled as defined in section 1382c of this title (with respect to States which are not eligible to participate in such program); and provide for flexibility in the application of such standards with respect to income by taking into account, except to the extent prescribed by the Secretary, the costs (whether in the form of insurance premiums or otherwise) incurred for medical care or for any other type of remedial care recognized under State law.” 42 U. S. C. § 1396a(a)(17).
  The SSI program, in turn, has its own eligibility requirements, which include “deeming” provisions. See 42 U. S. C. §§ 1382, 1382c(b), (f)(1).
  The States, if they choose to do so, may extend Medicaid coverage to the “medically needy.” 42 U. S. C. § 1396a(a)(10)(C); 42 CFR §§435.300-435.325, 435.800-435.845 (1980). Since Iowa does not extend Medicaid assistance to the medically needy, the Secretary’s deeming regulations applicable to this optional program are not at issue in this case. See 42 CFR §435.822 (1980).
  Title 42 CFR § 435.723 (1980) provides:
  “(a) If the agency provides Medicaid to SSI recipients, it must meet the requirements of this section in determining eligibility of aged, blind, and disabled individuals under the optional coverage provisions of §§435.210, 435.211, and 435.231.
  “(b) The agency must consider income and resources of spouses living in the same household as available to each other, whether or not they are actually contributed.
  “(c) If both spouses apply or are eligible as aged, blind, or disabled and cease to live together, the agency must consider their income and resources as available to each other for the first 6 months after the month they cease to live together. After this 6-month period, the agency must consider only the income and resources that are actually contributed by one spouse to the other.
  “(d) If only one spouse in a couple applies or is eligible and they cease to live together, the agency must consider only the income and resources of the ineligible spouse that are actually contributed to the eligible spouse after the month in which they cease to live together.”
  Elvina, therefore, is considered part of the optional categorically needy. 42 CFR §435.210 (1980).
  Petitioners’ challenge was based both on statutory and constitutional grounds. Petitioners contended that Iowa’s procedures were in conflict with § 1902(a)(17) of the Social Security Act and with the Secretary’s regulations, now codified at 42 CFR §435.723'(1980). Petitioners also contended that Iowa’s procedures violated the Equal Protection Clause and the Due Process Clause. Petitioners’ constitutional claims were not considered either by the District Court or by the Court of Appeals and are not before this Court.
  The District Court certified a class consisting of “all married couples residing in Iowa of which: (1) one spouse is eligible for Medicaid and requires institutionalization; and (2) the other spouse is not institutionalized; and (3) the non-institutionalized spouse has income which is, under current state procedures, being deemed available to the institutionalized spouse.” 443 F. Supp. 1315, 1320 (1978).
  45 CFR §248.3 (1976).
  Section 1902(a)(10)(A) requires a state Medicaid plan to provide
  “for making medical assistance available to all individuals receiving aid or assistance under any plan of the State approved under subchapter I, X, XIV, or XVI, or part A of subchapter IV of this chapter, or with respect to whom supplemental security income benefits are being paid under sub-chapter XVI of this chapter . . . .” 42 U. S. C. § 1396a(a)(10)(A) (emphasis added).
  Although we do not believe that § 1902(a)(10)(A) can be characterized as ambiguous in this regard, the legislative history of the original Medicaid statute is rather explicit in requiring the participating States to provide medical assistance to recipients under the four categorical welfare programs then in existence. “[A] State plan to be approved must include provision for medical assistance for all individuals receiving aid or assistance under State plans approved under titles I, IV, X, XIV, and XVI. It is only if this group is provided for that States may include medical assistance to the less needy.” S. Rep. No. 404, 89th Cong., 1st Sess., 77 (1965). Titles I, X, and XVI were respectively Old Age Assistance, Aid to the Blind, and Aid to the Permanently and Totally Disabled, the three categorical welfare programs replaced by SSI. See Schweiker v. Gray Panthers, 453 U. S. 34, 37-38, and nn. 1, 3 (1981). We find nothing in the adoption of the SSI program that would alter the meaning of § 1902(a)(10)(A).
  Section 1902(a)(17)(D) provides that the States’ standards for determining eligibility for, and the extent of, Medicaid assistance may “not take into account the financial responsibility of any individual for any applicant or recipient under the plan unless such applicant or recipient is such individual’s spouse or such individual’s child . . . .” 42 U. S. C. § 1396a(a)(17)(D).
  Respondents rely in particular on a portion of the 1965 Senate Report we quoted in Gray Panthers:
  “The committee believes it is proper to expect spouses to support each other and parents to be held accountable for the support of their minor children and their blind or permanently and totally disabled children.” S. Rep. No. 404, 89th Cong., 1st Sess., 78.
  Contrary to the dissent, we do not interpret subsection (17)(D) as "authorizing” the States to deem, without any limitation, income between spouses. That subsection simply prohibits the States from considering the financial responsibility of any individual for the Medicaid applicant unless that individual is the applicant’s spouse or parent. See nn. 1, 11, supra.
  As conceded by petitioners at oral argument, Tr. of Oral Arg. 9, Iowa is free to obtain reimbursement from the noninstitutionalized spouse in a lawsuit brought under its family responsibility laws. We recognize that such lawsuits may not be a uniformly practical alternative. See Schweiker v. Gray Panthers, 453 U. S., at 46.
  To a certain extent, therefore, the barriers Iowa faces in implementing its spousal responsibility policies are attributable to the choices it has made with regard to the Medicaid options available. Iowa has decided to become an SSI State rather than a § 209(b) State. The Secretary permits SSI States to opt for ‘“§ 209(b) status’ at any time.” Schweiker v. Gray Panthers, supra, at 39, n. 6. In addition, Iowa is subject to 42 CFR §435.723 (1980) only because it has decided to extend Medicaid assistance to the optional categorical needy. §435.700.