The US Court of Appeals for the Third Circuit recently clarified the standard of proof necessary to permit class certification. In In re: Hydrogen Peroxide Antitrust Litigation, No. 07-1689 (3d Cir. Dec. 31, 2008), the Third Circuit vacated a district court's decision to certify a class in a significant antitrust lawsuit, and held that the lower court had failed to resolve disputed issues concerning whether each requirement of Federal Rule of Civil Procedure 23 had been satisfied.