To determine the relationship among diaphragm, orbicularis oculi, and adductor pollicis blockade, train-of-four stimulation was applied to the phrenic, facial, and ulnar nerves in 16 adult patients anesthetized with alfentanil-propofol-oxygen. Vecuronium 0.04 or 0.07 mg/kg was given. The response of the adductor pollicis was measured with a force transducer, and that of the other muscles by electromyography (EMG). No statistically significant differences were detected with either dose in the intensity of maximum blockade measured at the three muscles. With 0.04 mg/kg, the first response (Tl) in the train-of-four was decreased (mean ± SEM) 78 ± 8, 62 ±11, and 84 ± 3% for the diaphragm, orbicularis oculi, and adductor pollicis, respectively. Corresponding values after 0.07 mg/kg were 95 ± 3, 82 ± 11, and 95 ± 2%, respectively. However, onset time was longer at the adductor pollicis than at the diaphragm, and the orbicularis oculi onset time approached that of the diaphragm. With 0.04 mg/kg, time to maximum diaphragmatic blockade was 2.9 ± 0.3 min, compared with 3.7 ± 0.6 min at the orbicularis oculi (no significant difference [NS]) and 6.6 ± 0.4 min at the adductor pollicis (P< 0.001). With vecuronium 0.07 mg/kg the values were 2.2 ± 0.3, 3.4 ± 0.5 (P= 0.024), and 6.3 ± 0.6 (P< 0.001), respectively. Time to 75% Tl recovery was similar at the diaphragm and the orbicularis oculi, but significantly longer at the adductor pollicis. The values were 14.6 ± 2.4, 17.8 ± 5.2 (NS), and 24.0 ± 2.8 min (P= 0.01), respectively, after 0.04 mg/kg, and were 26.0 ± 4.0, 28.7 ± 4.1 (NS), and 35.2 ± 4.0 min (P= 0.005), respectively, after 0.07 mg/kg. It is concluded that the orbicularis oculi response to facial stimulation reflects the extent of neuromuscular blockade of the diaphragm better than does the response of the adductor pollicis to ulnar nerve stimulation.