The efficacy, cycle control, subjective complaints, and safety of monophasic preparations of the oral contraceptives containing gestodene 75 mcg plus ethinyl estradiol 30 mcg versus desogestrel 150 mcg plus ethinyl estradiol 30 mcg were compared in a 6-cycle, open-label, parallel, randomized, multicenter phase IV clinical study in Latin America. Of a total of 176 women in each group, 163 in the gestodene group and 160 in the desogestrel group completed 6 cycles, providing data for 1,015 and 1,006 cycles, respectively. Subject compliance was excellent; pills were missed during only 6.9% of the cycles in each group. No woman became pregnant during the study. Gestodene group exhibited significantly better cycle control as evidenced by the lower incidence of breakthrough bleeding and spotting. Spotting in some cycles was reported by 11.9% of women taking the gestodene-combination compared with 21% of women taking the desogestrel-combination. Based on number of women, 86.4% of the gestodene group reported all cycles were normal (no BTB) compared with 76.7% of the desogestrel group. Also, the women in the gestodene group reported a significantly lower incidence of nuisance side effects during treatment cycles. No amenorrhea was observed for either group. There were no clinically significant differences between groups with respect to body weight, blood pressure, or laboratory evaluations. Seven women withdrew from the gestodene group and 8 women withdrew from the desogestrel group because of adverse reactions. The results of this study indicate that, although both OCs provided effective contraception, in comparison to the desogestrel-combination, the gestodene-containing OC is associated with better cycle control, less bleeding, and fewer subjective complaints.