Objective To compare the efficacy, side effects and acceptability of two Sino-implants with Norplant Methods A randomized, prospective multicenter comparative clinical study was conducted in 10 clinical centers in China. Results Totally 1 001, 1 000 and 998 cases were recruited for Sino-implant No. I, No. II and Norplant, respectively, in 1993. The follow-up rate was 99.8% totally in 5 years. Three and five pregnancies occurred respectively in Sino-implant No. I and No. II group, while no pregnancy occurred in the Norplant group. The cumulative pregnancy rate was 0.4, 0.7 and 0 per 100 women respectively in implant No.I, No. II and Norplant group for five years, meaning that there was no statistical difference. There was no ectopic pregnancy in the three groups. The cumulative discontinuation rates at the end of five years were not significantly different among the three groups, either. Men- strual problems were the main reason for termination. The menstrual blood loss decreased significantly and no serious health problems arose fromimplants use. Conclusion The two Sino-implants provided similar high efficacy and safety to Norplant, therefore, they can be used by women at reproductive age who are from different areas,different of races, educational background and occupation. Objective To compare the efficacy, side effects and acceptability of two Sino-implants with Norplant Methods A randomized, prospective multicenter comparative clinical study was conducted in 10 clinical centers in China. Results Totally 1 001, 1 000 and 998 cases were recruited for Sino- implant No. I, No. II and Norplant, respectively, in 1993. The follow-up rate was 99.8% totally in 5 years. Three and five pregnan are respectively in Sino-implant No. I and No. II group, while no The occurred pregnancy in the Norplant group. The cumulative pregnancy rate was 0.4, 0.7 and 0 per 100 women respectively in implant No. I, No. II and Norplant group for five years, meaning that there was no statistical difference. There was no ectopic pregnancy in the three groups. The cumulative discontinuation rates at the end of five years were not significantly different among the three groups, either. Men- strual problems were the main reason for termination. The menstrual blood loss dec Conclusion of the two Sino-implants provided similar high efficacy and safety to Norplant, therefore, they can be used by women at reproductive age who are from different areas, different of races, educational background and occupation.