To compare the characteriStics of the dose-response and the time-course of action between atracurium and veculonium, sixty Chinese patients, ASA grade I, aped 17~50 (28.2±8.3)years, scheduled for elective plastic surgery were studied. All the patients were randomly and equallydivided to either atracurium or vecuronium group. General anesthesia was maintained with 60%nitrous oxide in oxygen, thiopentone, and fentanyl. Neuromuscular function was assessed using anaccelerometer with tlain-of-four (TOF) stimulation at the wrist every 12 s, and the depressionpercentage of first botch (T1) was used as the study parameter. The dose-response relationships ofatracurium and vecuronium were determined by the cumulative dose-response technique. Accordingto the dose-response curves established by led squares linear regression, the neuromuscular blocking potency of atracurium was only approximately 17% that of vecuronium. There were significantdifferences in the ED50, ED90, and ED95 between the two drugs. After the intravenous administrationof equipotent doses of the two drugs (1.5×ED95), the duration of peak effect, clinical duration,recovery index, and total duration showed no significant differences between them. It is concluded thatatrscurium is a low-potency muscle relaxant and vecuronium is a high-potency muscle relaxant. Thepotency ratio of vecuronium:atracurium is 1:6 on the basis of ED95, and the recovery time course ofthe two drugs showed no significant differences following administration of equipotent doses.