Abney v. United States, supra, or a violation of his constitutional right to bail, Stack v. Boyle, 342 U. S. 1 (1951), because those situations, like the posting of security for costs involved in Cohen, “each involved an asserted right the legal and practical value of which could be destroyed if it were not vindicated before trial.” United States v. MacDonald, 435 U. S. 850, 860 (1978). By way of contrast, we have generally denied review of pretrial discovery orders, see, e. g., United States v. Ryan, supra; Cobbledick v. United States, supra. Our rationale has been that in the rare case when appeal after final judgment will not cure an erroneous discovery order, a party may defy the order, permit a contempt citation to be entered against him, and challenge the order on direct appeal of the contempt ruling. See Cobbledick v. United States, supra, at 327. We have also rejected immediate ap-pealability under § 1291 of claims that “may fairly be assessed” only after trial, United States v. MacDonald, supra, at 860, and those involving “considerations that are ‘enmeshed in the factual and legal issues comprising the plaintiff’s cause of action.’ ” Coopers & Lybrand v. Livesay, 437 U. S., at 469, quoting Mercantile National Bank v. Langdeau, 371 U. S. 555, 558 (1963).
An order refusing to disqualify counsel plainly falls within the large class of orders that are indeed reviewable on appeal after final judgment, and not within the much smaller class of those that are not. The propriety of the district court’s denial of a disqualification motion will often be difficult to assess until its impact on the underlying litigation may be evaluated, which is normally only after final judgment. The decision whether to disqualify an attorney ordinarily turns on the peculiar factual situation of the case then at hand, and the order embodying such a decision will rarely, if ever, represent a final rejection of a claim of fundamental right that cannot effectively be reviewed following judgment on the merits. In the case before us, petitioner has made no showing that its opportunity for meaningful review will perish