opinion: Per Curiam.
  Respondent Nelson sued in the United States District Court for the District of Colorado to compel arbitration of his discharge by petitioner Great Western Sugar Co. The District Court held that the presumption of arbitrability consistently applied by the Court of Appeals for the Tenth Circuit required that the dispute be submitted to arbitration. Before petitioner’s appeal from the District Court’s order could be decided on the merits, the arbitration proceedings had been completed, and respondent filed a suggestion of mootness with the Court of Appeals. The Court of Appeals, in an order and opinion admirable for its conciseness, if not for its fidelity to our case law, said:
  “This matter comes on for consideration of the appel-lee’s suggestion of mootness and motion to vacate judgment of the District Court and to remand the captioned cause with instructions to dismiss. The appellant filed a brief in response arguing that the appeal be allowed to continue but if not the judgment of the trial court should be reversed and the cause be remanded with directions to dismiss.
  “Upon consideration whereof, the order of the Court is as follows:
  “1. The appeal is dismissed on the ground of mootness.
  “2. The judgment of the trial court is allowed to stand.” App. to Pet. for Cert. A5.
  In Duke Power Co. v. Greenwood County, 299 U. S. 259, 267 (1936), this Court said:
  “Where it appears upon appeal that the controversy has become entirely moot, it is the duty of the appellate court to set aside the decree below and to remand the cause with directions to dismiss.” (Emphasis supplied.)
  The course of action prescribed in Duke Power has been followed in countless cases in this Court. See, e. g., Preiser v. Newkirk, 422 U. S. 395 (1975); Parker v. Ellis, 362 U. S. 574 (1960); United States v. Munsingwear, Inc., 340 U. S. 36 (1950).
  Here neither the law nor the facts are in dispute. The Court of Appeals has proceeded on the assumption that the case is moot and has dismissed the appeal for that reason. It has nonetheless stated that the judgment of the District Court shall remain in effect, a statement totally at odds with the holding of Duke Power. The reasons for not allowing the District Court judgment to remain in effect when the fact of mootness had been properly called to the attention of the Court of Appeals were fully stated in United States v. Munsingwear, Inc., supra, at 39-41, and need not be restated here. The Court of Appeals’ disposition of this case may-have been the result of a desire to show approval of the reasoning of the District Court in directing arbitration, but that motive cannot be allowed to excuse its failure to follow the teaching of Duke Power Co., supra.
  Because the fact of mootness is clear, and indeed is relied upon by the Court of Appeals as its reason for dismissing petitioner’s appeal, and because the law as laid down by this Court in Duke Power Co., supra, and United States v. Munsingwear, Inc., supra, is equally clear, the petition for certiorari is granted, the judgment of the Court of Appeals is vacated, and the case is remanded to the Court of Appeals with directions to vacate the District Court’s judgment and to remand the case for dismissal of respondent’s complaint.
  It is so ordered.
  United States v. Munsingwear, Inc., is perhaps the leading case on the proper disposition of cases that become moot on appeal. There the Court reiterated that “[t]he established practice of the Court in dealing with a civil case from a court in the federal system which has become moot while on its way here or pending our decision on the merits is to reverse or vacate the judgment below and remand with a direction to dismiss.” 340 U. S., at 39.
choices: comity: civil rights comity: criminal procedure comity: First Amendment comity: habeas corpus comity: military comity: obscenity comity: privacy comity: miscellaneous comity primarily removal cases, civil procedure (cf. comity, criminal and First Amendment); deference to foreign judicial tribunals assessment of costs or damages: as part of a court order Federal Rules of Civil Procedure including Supreme Court Rules, application of the Federal Rules of Evidence, Federal Rules of Appellate Procedure in civil litigation, Circuit Court Rules, and state rules and admiralty rules judicial review of administrative agency's or administrative official's actions and procedures mootness (cf. standing to sue: live dispute) venue no merits: writ improvidently granted no merits: dismissed or affirmed for want of a substantial or properly presented federal question, or a nonsuit no merits: dismissed or affirmed for want of jurisdiction (cf. judicial administration: Supreme Court jurisdiction or authority on appeal from federal district courts or courts of appeals) no merits: adequate non-federal grounds for decision no merits: remand to determine basis of state or federal court decision (cf. judicial administration: state law) no merits: miscellaneous standing to sue: adversary parties standing to sue: direct injury standing to sue: legal injury standing to sue: personal injury standing to sue: justiciable question standing to sue: live dispute standing to sue: parens patriae standing standing to sue: statutory standing standing to sue: private or implied cause of action standing to sue: taxpayer's suit standing to sue: miscellaneous judicial administration: jurisdiction or authority of federal district courts or territorial courts judicial administration: jurisdiction or authority of federal courts of appeals judicial administration: Supreme Court jurisdiction or authority on appeal or writ of error, from federal district courts or courts of appeals (cf. 753) judicial administration: Supreme Court jurisdiction or authority on appeal or writ of error, from highest state court judicial administration: jurisdiction or authority of the Court of Claims judicial administration: Supreme Court's original jurisdiction judicial administration: review of non-final order judicial administration: change in state law (cf. no merits: remand to determine basis of state court decision) judicial administration: federal question (cf. no merits: dismissed for want of a substantial or properly presented federal question) judicial administration: ancillary or pendent jurisdiction judicial administration: extraordinary relief (e.g., mandamus, injunction) judicial administration: certification (cf. objection to reason for denial of certiorari or appeal) judicial administration: resolution of circuit conflict, or conflict between or among other courts judicial administration: objection to reason for denial of certiorari or appeal judicial administration: collateral estoppel or res judicata judicial administration: interpleader judicial administration: untimely filing judicial administration: Act of State doctrine judicial administration: miscellaneous Supreme Court's certiorari, writ of error, or appeals jurisdiction miscellaneous judicial power, especially diversity jurisdiction