To compare the time course of neostigmine and pyridostigmine antagonism of profound neu- romuscular blockade (no-twitch: when no response to peripheral nerve stimulation could be elicited) induced by vecuronium, the authors studied 30 patients who were ASA Physical Status I or II undergoing minor surgery, free from neuromuscular, renal or hepatic dieases. Train-of Four[TOF] stimulation was applied to the ulnar nerve every ISseconds and the force of contraction of adductor pollicis muscle was recorded. In all patients, anesthesia was induced with thiopental sodium(5 mg/kg) and vecuronium (0.1 mg/kg), endotracheal intubation was performed at 100% depression of the T1(the first response in the train-of-four sequence). Patients were randomly assigned to one of two groups Five minutes after intubation, when there was no detectable twitch response, each patient received either neostigmine(0.03 mg/kg) with atropine sulfate(0.02 mg/kg). Neuromuscular fuction in another ten subjects were allowed to recover spontaneously. The results were as follows; 1) Profound neuromuscular blockade was not rapidly antagonized by either neostigmine or pyridostigmine but the use of anticholinesterase was effeetive for recovery. 2) The results demonstrated that there were no difference in antagonism of vecuronium induced profound neuromuscular block between neostigmine and pyridostigmine. 3) The time to 100% depression of T1 after vecuronium injection was 190.5+/-38.7 sec. 4) After anticholinesterase administration, in all groups, the changes of mean arterial pressure and heart rate were within +/-10% of control after anticholinesterase dministration were observed.