The effects of 3 anticholinesterases on rates of recovery from pancuronium-induced neuromuscular blockade were compared. Pancuronium (3 mg/70 kg) was antagonized during N2O-O2-halothane anesthesia, in man, with neostigmine (2.5 or 5.0 mg/70 kg), pyridostigmine (10 or 20 mg/70 kg) or edrophonium (50 or 100 mg/70 kg). Reversal was attempted at 10% spontaneous recovery of muscle twitch, which was measured by use of train-of-4 stimulation. Following administration of the antagonist each patient had progressive recovery of neuromuscular function. Recurarization was not observed during the period of study. Recovery was most rapid with edrophonium and slowest with pyridostigmine. At 5 min after administration of the antagonists, mean T4, the height of the 4th twitch as a percentage of the 1st in each train, exceeded 50% only with the larger dose of neostigmine and both doses of edrophonium. At 30 min after reversal there was no significant difference in recoveries among the drugs tested, and T4 exceeded 70% for all patients. Under the conditions of this study, neostigmine, pyridostigmine and edrophonium induce sustained antagonism of pancuronium-induced neuromuscular blockade. The antagonism produced by large doses of edrophonium is faster than that produced by neostigmine or pyridostigmine.