OBJECTIVE To compare the contraceptive efficacy of a new spermicide, bioadhesive nonoxynol (N-9) gel, with a traditional N-9 suppository. METHODS A total of 240 child-bearing aged woman volunteers were randomly divided into two groups: 120 cases using the gel for contraception, and another 120 using the suppository. Using lifetable method and log rank test, we compared the pregnancy rates and other discontinuation rates after follow-up for 6 months in two groups. RESULTS No abnormal findings of cervical smears were detected before and after this clinical trial in all 240 women. The follow-up rates at 6 months were 100.0% and 97.5% in the gel group and the suppository group, respectively. The 6-month gross cumulative pregnancy rates of typical use were 6.39 and 2.95 per 100 women (P > 0.05), respectively. If we eliminated the 5 pregnancy women (3 in the gel group, and 2 in the suppository one), who did not consistently use the spermisides for every intercourse, the cumulative pregnancy rates at 6 month in perfect use would be 3.71 and 2.03 (P > 0.05). And the discontinuation rates due to allergy or other side effects at 6 months in typical use were 3.45 and 4.57 (P > 0.05), respectively. All of the results observed between two groups in this study were not statistically significant. CONCLUSIONS The contraceptive efficacy of bioadhesive N-9 gel is as same as that of the N-9 suppository, and its clinical use is quite safe.