In a large and open prospective multicenter trial of 12,250 cycles from 2,378 women, contraceptive efficacy, clinical tolerance and acceptability of a new monophasic contraceptive combination containing 75 mcg gestodene (delta-5-levonorgestrel) and 30 mcg ethinyl oestradiol were studied. The objective was to assess efficacy, safety, side effects and cycle control of this oral contraceptive on healthy women using no other additional birth control methods. Two women became pregnant (0.016%) during the trial; both were patient failures. There was no effect on systolic or diastolic pressures. An average weight increase of 0.3 kg was noted. Cycle control was excellent with 95% of the cycles free of spotting and 98% free of breakthrough bleeding after six cycles. No serious complications occurred. There was an overall incidence of 14% reported side effects (after six cycles), indicating that the hormonal combination is well tolerated. It should be noted that 41.4% of the patients had some complaint before starting the treatment. For all complaints, a highly significant improvement was seen during the treatment.