Objective To compare the time-course of relaxant effect of rocuronium between patients of Uygur and Han nationalities.Methods Thirty ASA Ⅰ or Ⅱ patients (15 Uygur nationality,15 Han nationality) of both sexes,aged 20-55 yr weighing 45-73 kg were divided into 2 groups (n=15 each):group U Uygur nationality and group H Han nationality.Anesthesia was induced with midazolam,propofol,fentanyl and suxamethonium chloride.Tracheal intubation was performed and the patients were mechanically ventilated.Recuronium 0.6mg/kg was then given iv.Neuromuscular function was monitored with acceleromyograph using single stimulation of the ulna nerve.The onset time (time from injection of recuronium to maximal paralysis),nonresponse time (duration of maximal twitch depression),clinical duration (time required for the twitch to return to 25% of control height after injection of initial dose),75%recovery time (time for twitch to return to 75%of control height after injection of initial dose) and recovery index (time for twitch height to return from 25% to 75% of control height) were recorded.Results There was no significant difference in the onset time between the two nationalities.The time of nonresponse period,clinical duration and 75% recovery time were significantly shorter in Uygur patients than in Han patients.Recovery index was significantly shorter in Uygur patients.Conclusion There is a significant difference in the time-course of muscle relaxant effect of recuronium between Uygur and Han nationalities.The influence of nationality on recommended dosage of recuronimn should be considered.