目的　比较两种小剂量米非司酮用于紧急避孕的有效性、副反应和对月经的影响。方法　征集无保护性性交在避孕失败后 72h内来院就诊的健康妇女 180例 ,随机分为两组 ,A组一次性服用米非司酮 2 5mg ,B组一次性服用米非司酮 10mg ,服药后按时随访并观察药物副反应及下次月经情况 ,保证月经复潮前禁欲或采用避孕套避孕。结果　两组避孕有儿率分别为 86 .76 %和 85 .96 % ,P >0 .0 5 ,差异无显著意义 ,各种副反应发生率较低 ,均在 10 %以内 ,两组相近 ,月经趋于正常者两组分别为 73.4 %和 76 .7% ,P >0 .0 5。结论　两种小剂量米非司酮 (2 5mg和 10mg)用于紧急避孕同样是安全、有效的 Objective To compare the effectiveness of two low-dose mifepristone for emergency contraception, side effects and the effects on menstruation. Methods One hundred and eighty healthy women who were hospitalized within 72 hours after failure of contraception were enrolled in this study. They were randomly divided into two groups: group A took 25 mg of mifepristone once, group B took mifepristone 10 mg once, After follow-up on time and observe the side effects of drugs and the next menstrual situation, to ensure that before menstrual cramps abstinence or condom contraception. Results There were 86.76% and 85.96% of contraception in both groups, P> 0.05, the difference was not significant, the incidence of various side effects was low, both within 10%, the two groups were similar, Menstrual tenients were normal in both groups were 73.4% and 76.7%, P> 0.05. Conclusions Two small doses of mifepristone (25 mg and 10 mg) are equally safe and effective for emergency contraception