The aim of the trial was to demonstrate the contraceptive efficacy of a new low dose oral contraceptive containing 20 micrograms ethinyl estradiol and 100 micrograms levonorgestrel and to observe cycle control and safety. Data from 805 treated women resulted in 4400 treatment cycles. One pregnancy occurred while on the trial medication as a result of method failure, resulting in a Pearl index of 0.29. Cycle control was good, and cycle length as well as duration and intensity of withdrawal bleeding were not significantly changed during the trial. Intermenstrual bleeding usually occurred as spotting and decreased considerably during the treatment phase. Spotting alone was reported in 12.4% of cycles, breakthrough bleeding alone in 4.5% of cycles, and breakthrough bleeding and spotting together in 1.4% of treatment cycles. The rate of absence of withdrawal bleeding declined throughout the trial to 2.4% in cycle 6. There were no serious adverse events related to treatment, and most adverse events were those commonly observed in clinical trials with oral contraceptives. Headache, breast tension, and nausea were reported by 17.3%, 11.0%, and 7.7% of the women, respectively. There were no clinically relevant changes in laboratory parameters, blood pressure, or weight. In this trial, the new low dose oral contraceptive containing 20 micrograms ethinyl estradiol and 100 micrograms levonorgestrel was shown to be effective, safe, and well tolerated. Cycle control was found to be good and there was a low incidence of adverse events.