Efficacy, cycle control, tolerance, and adverse events were studied in a clinical Phase IV study using a new progestogen, gestodene, in an amount of 75 micrograms combined with 30 micrograms ethinylestradiol. The study was performed as a multicenter trial in 96,000 patients over a period of 6 cycles. Half of the patients taking the new preparation were first-time OC users, the other half switched from another OC. With regard to contraceptive efficacy, the life-table analysis showed a value of 0.032% for method failure and 0.114% for patient failure. The correspondent Pearl-Index is 0.062 and 0.22. The new drug was found acceptable by more than 90% of the women involved in the trial. Dysmenorrhea present in the "switchers" mostly disappeared on the new OC, while body weight and blood pressure remained virtually unchanged. Thus, it can be concluded that blood pressure and body weight behaviour is similar to that seen with other low-dose OCs. The new combined pill offers excellent cycle stability and has a very favourable effect on dysmenorrhea. The number of clinically diagnosed thrombotic events documented in this study was 0.65 per 1000 woman-years (TWY) and does not exceed the range of events seen in groups of women using non-hormonal methods of contraception (Oxford-FPA study 0.4/TWY and RCGP study 0.8/TWY).