Combination of pancuronium and metocurine or pancuronium and d-tubocurarine produces potentiation of neuromuscular blocking effects such that administration of relatively small doses of these drugs can yield clinically effective neuromuscular blockade. The clinical characteristics of the block produced in A.S.A. class I-II patients during N2O-narcotic-thiopental anesthesia by the pancuronium-metocurine combination at the calculated ED95 (N = 8) and at twice the ED95 (N = 9) were compared with the block produced by pancuronium alone at its ED95 (N = 20) and at twice the ED95 (N = 6). Onset time (from drug injection to 95% twitch suppression) and the maximum twitch depression achieved were comparable between corresponding groups, but the 25% recovery time (from drug injection to 25% recovery of twitch height) was significantly shorter in the groups that received the pancuronium-metocurine combination. Furthermore, at twice the ED95, heart rate increased significantly more in the pancuronium group than in the pancuronium-metocurine combination group. Mean systemic blood pressure did not change significantly in either group. We conclude that patients given a combination of pancuronium and metocurine in large doses experience less hemodynamic change and more rapid recovery of neuromuscular function than do patients given equivalent doses of pancuronium alone.