OBJECTIVE To assess the contraceptive reliability, cycle control and tolerability of a new monophasic oral contraceptive containing 30 g ethinylestradiol plus 3 mg drospirenone (Yasmin, Schering AG, Berlin, Germany), it was compared with an established oral contraceptive containing 30 g ethinylestradiol plus 150 g desogestrel (Marvelon, NV Organon, Oss, The Netherlands). METHODS A randomized, open-label, 13-cycle study was performed at 80 European centers. Contraceptive reliability, cycle control, blood pressure, body weight, the incidence of adverse events and skin condition were assessed during 13 cycles of oral contraceptive use, and at follow-up. Subjects recorded body weight on three consecutive days pretreatment and weekly thereafter. RESULTS Of 2069 women who started the study and received the trial preparations in a ratio of 4:1 (ethinylestradiol/drospirenone, n = 1657; ethinylestradiol/desogestrel, n = 412), 1615 completed the 13 cycles plus follow-up, providing data for over 23,000 evaluable cycles. Eleven pregnancies occurred during treatment, only one of which (in the ethinylestradiol/drospirenone group) could not be ascribed to user failure or interaction with other factors. Both preparations provided effective contraception and cycle control. Pre-existing acne and seborrhea were improved and blood pressure was essentially unchanged. The two treatments differed in their effect on body weight, the difference being statistically significant. In the ethinylestradiol/drospirenone group, there was a distinct decrease over the whole treatment phase, while a subtle and less distinct decrease was documented in the ethinylestradiol/desogestrel group. CONCLUSIONS The combination of 30 g ethinylestradiol/3 mg drospirenone provides effective oral contraception, excellent cycle control, good tolerability and a level of weight loss that may have a significant beneficial effect on compliance in women with a tendency to weight gain due to water retention.