Lidocaine, considered by some to be potentially dangerous in malignant hyperthermia (MH), was administered intravenously to a dose of 15 mg/kg to five conscious MH-susceptible pigs. Subsequently the same pigs were given 24 mg/kg intravenously over a period of 2 hours after being anesthetized with thiopental. All animals developed systemic toxicity to lidocaine but without evidence of MH. Prior administration of lidocaine did not prevent development of subsequent MH due to succinylcholine and halothane. Lidocaine is safe in porcine MH.