Buffalo Pharmaceutical Company (defendant) purchased drugs from manufacturers, repackaged them, and shipped them to physicians and others under its own labels. On at least two occasions, the drug manufacturer’s labels were incorrect. Buffalo Pharmaceutical and its president and general manager, Dotterweich (defendant), were prosecuted for shipping misbranded or adulterated products in interstate commerce in violation of § 301 of the Federal Food, Drug, and Cosmetic Act. After a trial in federal district court, the jury acquitted Buffalo Pharmaceutical but convicted Dotterweich, who was sentenced to probation for 60 days and assessed a fine. Dotterweich appealed, and the court of appeals reversed the conviction. The United States Supreme Court granted certiorari to review.