opinion: Justice Rehnquist
  delivered the opinion of the Court.
  Respondent Rosa Elvira Montoya de Hernandez was detained by customs officials upon her arrival at the Los Ange-les Airport on a flight from Bogota, Colombia. She was found to be smuggling 88 cocaine-filled balloons in her alimentary canal, and was convicted after a bench trial of various federal narcotics offenses. A divided panel of the United States Court of Appeals for the Ninth Circuit reversed her convictions, holding that her detention violated the Fourth Amendment to the United States Constitution because the customs inspectors did not have a “clear indication” of alimentary canal smuggling at the time she was detained. 731 F. 2d 1369 (1984). Because of a conflict in the decisions of the Courts of Appeals on this question and the importance of its resolution to the enforcement of customs laws, we granted certiorari. 469 U. S. 1188. We now reverse.
  Respondent arrived at Los Angeles International Airport shortly after midnight, March 5, 1983, on Avianca Flight 080, a direct 10-hour flight from Bogota, Colombia. Her visa was in order so she was passed through Immigration and proceeded to the customs desk. At the customs desk she encountered Customs Inspector Talamantes, who reviewed her documents and noticed from her passport that she had made at least eight recent trips to either Miami or Los Angeles. Talamantes referred respondent to a secondary customs desk for further questioning. At this desk Talamantes and another inspector asked respondent general questions concerning herself and the purpose of her trip. Respondent revealed that she spoke no English and had no family or friends in the United States. She explained in Spanish that she had come to the United States to purchase goods for her husband’s store in Bogota. The customs inspectors recognized Bogota as a “source city” for narcotics. Respondent possessed $5,000 in cash, mostly $50 bills, but had no billfold. She indicated to the inspectors that she had no appointments with merchandise vendors, but planned to ride around Los Angeles in taxicabs visiting retail stores such as J. C. Penney and K-Mart in order to buy goods for her husband’s store with the $5,000.
  Respondent admitted that she had no hotel reservations, but stated that she planned to stay at a Holiday Inn. Respondent could not recall how her airline ticket was purchased. When the inspectors opened respondent’s one small valise they found about four changes of “cold weather” clothing. Respondent had no shoes other than the high-heeled pair she was wearing. Although respondent possessed no checks, waybills, credit cards, or letters of credit, she did produce a Colombian business card and a number of old receipts, waybills, and fabric swatches displayed in a photo album.
  At this point Talamantes and the other inspector suspected that respondent was a “balloon swallower,” one who attempts to smuggle narcotics into this country hidden in her alimentary canal. Over the years Inspector Talamantes had apprehended dozens of alimentary canal smugglers arriving on Avianca Flight 080. See App. 42; United States v. Mendez-Jimenez, 709 F. 2d 1300, 1301 (CA9 1983).
  The inspectors requested a female customs inspector to take respondent to a private area and conduct a patdown and strip search. During the search the female inspector felt respondent’s abdomen area and noticed a firm fullness, as if respondent were wearing a girdle. The search revealed no contraband, but the inspector noticed that respondent was wearing two pairs of elastic underpants with a paper towel lining the crotch area.
  When respondent returned to the customs area and the female inspector reported her discoveries, the inspector in charge told respondent that he suspected she was smuggling drugs in her alimentary canal. Respondent agreed to the inspector’s request that she be x-rayed at a hospital but in answer to the inspector’s query stated that she was pregnant. She agreed to a pregnancy test before the x ray. Respondent withdrew the consent for an x ray when she learned that she would have to be handcuffed en route to the hospital. The inspector then gave respondent the option of returning to Colombia on the next available flight, agreeing to an x ray, or remaining in detention until she produced a monitored bowel movement that would confirm or rebut the inspectors’ suspicions. Respondent chose the first option and was placed in a customs office under observation. She was told that if she went to the toilet she would have to use a wastebasket in the women’s restroom, in order that female customs inspectors could inspect her stool for balloons or capsules carrying narcotics. The inspectors refused respondent’s request to place a telephone call.
  Respondent sat in the customs office, under observation, for the remainder of the night. During the night customs officials attempted to place respondent on a Mexican airline that was flying to Bogota via Mexico City in the morning. The airline refused to transport respondent because she lacked a Mexican visa necessary to land in Mexico City. • Respondent was not permitted to leave, and was informed that she would be detained until she agreed to an x ray or her bowels moved. She remained detained in the customs office under observation, for most of the time curled up in a chair leaning to one side. She refused all offers of food and drink, and refused to use the toilet facilities. The Court of Appeals noted that she exhibited symptoms of discomfort consistent with “heroic efforts to resist the usual calls of nature.” 731 F. 2d, at 1371.
  At the shift change at 4:00 o’clock the next afternoon, almost 16 hours after her flight had landed, respondent still had not defecated or urinated or partaken of food or drink. At that time customs officials sought a court order authorizing a pregnancy test, an x ray, and a rectal examination. The Federal Magistrate issued an order just before midnight that evening, which authorized a rectal examination and involuntary x ray, provided that the physician in charge considered respondent’s claim of pregnancy. Respondent was taken to a hospital and given a pregnancy test, which later turned out to be negative. Before the results of the pregnancy test were known, a physician conducted a rectal examination and removed from respondent’s rectum a balloon containing a foreign substance. Respondent was then placed formally under arrest. By 4:10 a. m. respondent had passed 6 similar balloons; over the next four days she passed 88 balloons containing a total of 528 grams of 80% pure cocaine hydrochloride.
  After a suppression hearing the District Court admitted the cocaine in evidence against respondent. She was convicted of possession of cocaine with intent to distribute, 21 U. S. C. § 841(a)(1), and unlawful importation of cocaine, 21 U. S. C. §§ 952(a), 960(a).
  A divided panel of the United States Court of Appeals for the Ninth Circuit reversed respondent’s convictions. The court noted that customs inspectors had a “justifiably high level of official skepticism” about respondent’s good motives, but the inspectors decided to let nature take its course rather than seek an immediate magistrate’s warrant for an x ray. 731 F. 2d, at 1372. Such a magistrate’s warrant required a “clear indication” or “plain suggestion” that the traveler was an alimentary canal smuggler under previous decisions of the Court of Appeals. See United States v. Quintero-Castro, 705 F. 2d 1099 (CA9 1983); United States v. Mendez-Jimenez, 709 F. 2d 1300, 1302 (CA9 1983); but cf. South Dakota v. Opperman, 428 U. S. 364, 370, n. 5 (1976). The court applied this required level of suspicion to respondent’s case. The court questioned the “humanity” of the inspectors’ decision to hold respondent until her bowels moved, knowing that she would suffer “many hours of humiliating discomfort” if she chose not to submit to the x-ray examination. The court concluded that under a “clear indication” standard “the evidence available to the customs officers when they decided to hold [respondent] for continued observation was insufficient to support the 16-hour detention.” 731 F. 2d, at 1373.
  The Government contends that the customs inspectors reasonably suspected that respondent was an alimentary canal smuggler, and this suspicion was sufficient to justify the detention. In support of the judgment below respondent argues, inter alia, that reasonable suspicion would not support respondent’s detention, and in any event the inspectors did not reasonably suspect that respondent was carrying narcotics internally.
  The Fourth Amendment commands that searches and seizures be reasonable. What is reasonable depends upon all of the circumstances surrounding the search or seizure and the nature of the search or seizure itself. New Jersey v. T. L. O., 469 U. S. 325, 337-342 (1985). The permissibility of a particular law enforcement practice is judged by “balancing its intrusion on the individual’s Fourth Amendment interests against its promotion of legitimate governmental interests.” United States v. Villamonte-Marquez, 462 U. S. 579, 588 (1983); Delaware v. Prouse, 440 U. S. 648, 654 (1979); Camara v. Municipal Court, 387 U. S. 523 (1967).
  Here the seizure of respondent took place at the international border. Since the founding of our Republic, Congress has granted the Executive plenary authority to conduct routine searches and seizures at the border, without probable cause or a warrant, in order to regulate the collection of duties and to prevent the introduction of contraband into this country. See United States v. Ramsey, 431 U. S. 606, 616-617 (1977), citing Act of July 31, 1789, ch. 5, 1 Stat. 29. This Court has long recognized Congress’ power to police entrants at the border. See Boyd v. United States, 116 U. S. 616, 623 (1886). As we stated recently:
  “‘Import restrictions and searches of persons or packages at the national border rest on different considerations and different rules of constitutional law from domestic regulations. The Constitution gives Congress broad comprehensive powers “[t]o regulate Commerce with foreign Nations,” Art. I, §8, cl. 3. Historically such broad powers have been necessary to prevent smuggling and to prevent prohibited articles from entry.’” Ramsey, supra, at 618-619, quoting United States v. 12 200-Ft. Reels of Film, 413 U. S. 123, 125 (1973).
  Consistently, therefore, with Congress’ power to protect the Nation by stopping and examining persons entering this country, the Fourth Amendment’s balance of reasonableness is qualitatively different at the international border than in the interior. Routine searches of the persons and effects of entrants are not subject to any requirement of reasonable suspicion, probable cause, or warrant, and first-class mail may be opened without a warrant on less than probable cause, Ramsey, supra. Automotive travelers may be stopped at fixed checkpoints near the border -without individualized suspicion even if the stop is based largely on ethnicity, United States v. Martinez-Fuerte, 428 U. S. 543, 562-563 (1976), and boats on inland waters with ready access to the sea may be hailed and boarded with no suspicion whatever. United States v. Villamonte-Marquez, supra.
  These cases reflect longstanding concern for the protection of the integrity of the border. This concern is, if anything, heightened by the veritable national crisis in law enforcement caused by smuggling of illicit narcotics, see United States v. Mendenhall, 446 U. S. 544, 561 (1980) (Powell, J., concurring), and in particular by the increasing utilization of alimentary canal smuggling. This desperate practice appears to be a relatively recent addition to the smugglers’ repertoire of deceptive practices, and it also appears to be exceedingly difficult to detect. Congress had recognized these difficulties. Title 19 U. S. C. § 1582 provides that “all persons coming into the United States from foreign countries shall be liable to detention and search authorized . . . [by customs regulations].” Customs agents may “stop, search, and examine” any “vehicle, beast or person” upon which an officer suspects there is contraband or “merchandise which is subject to duty.” §482; see also §§ 1467, 1481; 19 CFR §§ 162.6, 162.7 (1984).
  Balanced against the sovereign’s interests at the border are the Fourth Amendment rights of respondent. Having presented herself at the border for admission, and having subjected herself to the criminal enforcement powers of the Federal Government, 19 U. S. C. § 482, respondent was entitled to be free from unreasonable search and seizure. But not only is the expectation of privacy less at the border than in the interior, see, e. g., Carroll v. United States, 267 U. S. 132, 154 (1925); cf. Florida v. Royer, 460 U. S. 491, 515 (1983) (Blackmun, J., dissenting), the Fourth Amendment balance between the interests of the Government and the privacy right of the individual is also struck much more favorably to the Government at the border. Supra, at 538.
  We have not previously decided what level of suspicion would justify a seizure of an incoming traveler for purposes other than a routine border search. Cf. Ramsey, 431 U. S., at 618, n. 13. The Court of Appeals held that the initial detention of respondent was permissible only if the inspectors possessed a “clear indication” of alimentary canal smuggling. 731 F. 2d, at 1372, citing United States v. Quintero-Castro, 705 F. 2d 1099 (CA9 1983); cf. United States v. Mendez-Jimenez, 709 F. 2d 1300 (CA9 1983). This “clear indication” language comes from our opinion in Schmerber v. California, 384 U. S. 757 (1966), but we think that the Court of Appeals misapprehended the significance of that phrase in the context in which it was used in Schmerber. The Court of Appeals viewed “clear indication” as an intermediate standard between “reasonable suspicion” and “probable cause.” See Mendez-Jimenez, supra, at 1302. But we think that the words in Schmerber were used to indicate the necessity for particularized suspicion that the evidence sought might be found within the body of the individual, rather than as enunciating still a third Fourth Amendment threshold between “reasonable suspicion” and “probable cause.”
  No other court, including this one, has ever adopted Schmerber1 s “clear indication” language as a Fourth Amendment standard. See, e. g., Winston v. Lee, 470 U. S. 753, 759-763 (1985) (surgical removal of bullet for evidence). Indeed, another Court of Appeals, faced with facts almost identical to this case, has adopted a less strict standard based upon reasonable suspicion. See United States v. Mosquera-Ramirez, 729 F. 2d 1352, 1355 (CA11 1984). We do not think that the Fourth Amendment’s emphasis upon reasonableness is consistent with the creation of a third verbal standard in addition to “reasonable suspicion” and “probable cause”; we are dealing with a constitutional requirement of reasonableness, not mens rea, see United States v. Bailey, 444 U. S. 394, 403-406 (1980), and subtle verbal gradations may obscure rather than elucidate the meaning of the provision in question.
  We hold that the detention of a traveler at the border, beyond the scope of a routine customs search and inspection, is justified at its inception if customs agents, considering all the facts surrounding the traveler and her trip, reasonably suspect that the traveler is smuggling contraband in her alimentary canal.
  The “reasonable suspicion” standard has been applied in a number of contexts and effects a needed balance between private and public interests when law enforcement officials must make a limited intrusion on less than probable cause. It thus fits well into the situations involving alimentary canal smuggling at the border: this type of smuggling gives no external signs and inspectors will rarely possess probable cause to arrest or search, yet governmental interests in stopping smuggling at the border are high indeed. Under this standard officials at the border must have a “particularized and objective basis for suspecting the particular person” of alimentary canal smuggling. United States v. Cortez, 449 U. S. 411, 417 (1981); id., at 418, citing Terry v. Ohio, 392 U. S. 1, 21, n. 18 (1968).
  The facts, and their rational inferences, known to customs inspectors in this case clearly supported a reasonable suspicion that respondent was an alimentary canal smuggler. We need not belabor the facts, including respondent’s implausible story, that supported this suspicion, see supra, at 533-536. The trained customs inspectors had encountered many alimentary canal smugglers and certainly had more than an “inchoate and unparticularized suspicion or ‘hunch,’” Terry, supra, at 27, that respondent was smuggling narcotics in her alimentary canal. The inspectors’ suspicion was a “‘common-sense conclusio[n] about human behavior’ upon which ‘practical people,’ — including government officials, are entitled to rely.” T. L. O., 469 U. S., at 346, citing United States v. Cortez, supra.
  The final issue in this case is whether the detention of respondent was reasonably related in scope to the circumstances which justified it initially. In this regard we have cautioned that courts should not indulge in “unrealistic second-guessing,” United States v. Sharpe, 470 U. S. 675, 686 (1985), and we have noted that “creative judge[s], engaged in post hoc evaluations of police conduct can almost always imagine some alternative means by which the objectives of the police might have been accomplished.” Id., at 686-687. But “[t]he fact that the protection of the public might, in the abstract, have been accomplished by ‘less intrusive’ means does not, in itself, render the search unreasonable.” Id., at 687, citing Cady v. Dombrowski, 413 U. S. 433, 447 (1973). Authorities must be allowed “to graduate their response to the demands of any particular situation.” United States v. Place, 462 U. S. 696, 709, n. 10 (1983). Here, respondent was detained incommunicado for almost 16 hours before inspectors sought a warrant; the warrant then took a number of hours to procure, through no apparent fault of the inspectors. This length of time undoubtedly exceeds any other detention we have approved under reasonable suspicion. But we have also consistently rejected hard-and-fast time limits, Sharpe, supra; Place, supra, at 709, n. 10. Instead, “common sense and ordinary human experience must govern over rigid criteria.” Sharpe, supra, at 685.
  The rudimentary knowledge of the human body which judges possess in common with the rest of humankind tells us that alimentary canal smuggling cannot be detected in the amount of time in which other illegal activity may be investigated through brief Terry-type stops. It presents few, if any external signs; a quick frisk will not do, nor will even a strip search. In the case of respondent the inspectors had available, as an alternative to simply awaiting her bowel movement, an x ray. They offered her the alternative of submitting herself to that procedure. But when she refused that alternative, the customs inspectors were left with only two practical alternatives: detain her for such time as necessary to confirm their suspicions, a detention which would last much longer than the typical Terry stop, or turn her loose into the interior carrying the reasonably suspected contraband drugs.
  The inspectors in this case followed this former procedure. They no doubt expected that respondent, having recently disembarked from a 10-hour direct flight with a full and stiff abdomen, would produce a bowel movement without extended delay. - But her visible efforts to resist the call of nature, which the court below labeled “heroic,” disappointed this expectation and in turn caused her humiliation and discomfort. Our prior cases have refused to charge police with delays in investigatory detention attributable to the suspect’s evasive actions, see Sharpe, 470 U. S., at 687-688; id., at 697 (Marshall, J., concurring in judgment), and that principle applies here as well. Respondent alone was responsible for much of the duration and discomfort of the seizure.
  Under these circumstances, we conclude that the detention in this case was not unreasonably long. It occurred at the international border, where the Fourth Amendment balance of interests leans heavily to the Government. At the border, customs officials have more than merely an investigative law enforcement role. They are also charged, along with immigration officials, with protecting this Nation from entrants who may bring anything harmful into this country, whether that be communicable diseases, narcotics, or explosives. See 8 U. S. C. §§ 1182(a)(23), 1182(a)(6), 1222; 19 CFR §§ 162.4-162.7 (1984). See also 19 U. S. C. §482; 8 U. S. C. § 1103(a). In this regard the detention of a suspected alimentary canal smuggler at the border is analogous to the detention of a suspected tuberculosis carrier at the border: both are detained until their bodily processes dispel the suspicion that they will introduce a harmful agent into this country. Cf. 8 U. S. C. § 1222; 42 CFR pt. 34 (1984); 19 U. S. C. §§482, 1582.
  Respondent’s detention was long, uncomfortable, indeed, humiliating; but both its length and its discomfort resulted solely from the method by which she chose to smuggle illicit drugs into this country. In Adams v. Williams, 407 U. S. 143 (1972), another Terry-stop case, we said that “[t]he Fourth Amendment does not require a policeman who lacks the precise level of information necessary for probable cause to arrest to simply shrug his shoulders and allow a crime to occur or a criminal to escape.” Id., at 145. Here, by analogy, in the presence of articulable suspicion of smuggling in her alimentary canal, the customs officers were not required by the Fourth Amendment to pass respondent and her 88 cocaine-filled balloons into the interior. Her detention for the period of time necessary to either verify or dispel the suspicion was not unreasonable. The judgment of the Court of Appeals is therefore
  Reversed.
  See United States v. Ramsey, 431 U. S., at 616-619; Almeida-Sanchez v. United States, 413 U. S. 266, 272-273 (1973); id., at 288 (White, J., dissenting). As the Court stated in Carroll v. United States, 267 U. S. 132, 154 (1925):
  “Travellers may be so stopped in crossing an international boundary because of national self protection reasonably requiring one entering the country to identify himself as entitled to come in and his belongings as effects which may be lawfully brought in.”
  See United States v. DeMontoya, 729 F. 2d 1369 (CA11 1984) (required surgery; swallowed 100 cocaine-filled condoms); United States v. Pino, 729 F. 2d 1357 (CA11 1984) (required surgery; 120 cocaine-filled pellets); United States v. Mejia, 720 F. 2d 1378 (CA5 1983) (75 balloons); United States v. Couch, 688 F. 2d 599, 605 (CA9 1982) (36 capsules); United States v. Quintero-Castro, 705 F. 2d 1099 (CA9 1983) (120 balloons); United States v. Saldarriaga-Marin, 734 F. 2d 1425 (CA11 1984); United States v. Vega-Barvo, 729 F. 2d 1341 (CA11 1984) (135 condoms); United States v. Mendez-Jimenez, 709 F. 2d 1300 (CA9 1983) (102 balloons); United States v. Mosquera-Ramirez, 729 F. 2d 1352 (CA11 1984) (95 condoms); United States v. Castrillon, 716 F. 2d 1279 (CA9 1983) (83 balloons); United States v. Castaneda-Castaneda, 729 F. 2d 1360 (CA11 1984) (2 smugglers; 201 balloons); United States v. Caicedo-Guamizo, 723 F. 2d 1420 (CA9 1984) (85 balloons); United States v. Henao-Castano, 729 F. 2d 1364 (CA11 1984) (85 condoms); United States v. Ek, 676 F. 2d 379 (CA9 1982) (30 capsules); United States v. Padilla, 729 F. 2d 1367 (CA11 1984) (115 condoms); United States v. Gomez-Diaz, 712 F. 2d 949 (CA5 1983) (69 balloons); United States v. D’Allerman, 712 F. 2d 100 (CA5 1983) (80 balloons); United States v. Contento-Pachon, 723 F. 2d 691 (CA9 1984) (129 balloons).
  In that ease we stated:
  “The interests in human dignity and privacy which the Fourth Amendment protects forbid any such intrusion [beyond the body’s surface] on the mere chance that desired evidence might be obtained. In the absence of a clear indication that in fact such evidence will be found, these fundamental human interests require law officers to suffer the risk that such evidence may disappear unless there is an immediate search.” 384 U. S., at 769-770.
  It is also important to note what we do not hold. Because the issues are not presented today we suggest no view on what level of suspicion, if any, is required for nonroutine border searches such as strip, body-cavity, or involuntary x-ray searches. Both parties would have us decide the issue of whether aliens possess lesser Fourth Amendment rights at the border; that question was not raised in either court below and we do not consider it today.