Objective To evaluate the influence of age factors on etomidate sedative potency.Methods One hundred and fifty (ASA physical status Ⅰ or Ⅱ) patients of both sexes,scheduled for elective operation under general anesthesia,were divided into 3 groups according to age (n =50 each):group Y 18-44 yr,group M 40-64 yr and group O 65-75 yr.Each group was randomly divided into 5 subgroups receiving in'venous etomidate 0.07,0.09,0.11,0.13 and 0.17 mg/kg,respectively.Loss of consciousness was evaluated depending on loss of eyelash reflex within 5 min after intravenous administration.Results ED50 of etomidate inducing loss of consciousness was 0.13,0.11 and 0.09 mg/kg in group Y,M and O,respectively.Compared with that in group Y,ED50 was significantly decreased in group O,however,and showed no significant change in group M.Conclusion Age factors can affect sedative potency of etomidate,which appears greater in the elderly patients.