To evaluate the effects of Diane-35 on androgenized oligomenorrheic women with polycystic ovarian syndrome, 32 women with PCOS were recruited to an open study of one-year duration. The effects of Diane-35 on signs of androgenization and on morphological and hormonal parameters were assessed in the pre- and posttreatment cycles and in the 3rd, 6th, 9th, and 12th treatment cycles. Twenty-two women completed the 12-month study period, five withdrew due to adverse events, two were lost to follow-up, and three stopped early because of a lack of efficacy. Ultrasound demonstrated significant reductions in ovarian volume, stromal density, and follicle number and size. Serum concentrations of LH, FSH, testosterone, androstenedione, and dehydroepiandrosterone sulfate decreased, and serum SHBG increased significantly. Mean Ferriman-Gallwey hirsutism scores declined from 14.3 before treatment to 5.7 at completion of therapy. Severe facial hirsutism, present in 23 (71.9%) of 32 women, disappeared in 6 women and improved in 6 women--a healing/improvement rate of 54.6% of 22 women who completed the study. Cycle control was good, amenorrhea occurred in 5 (1.6%) of 322 treatment cycles, while 94.8% of withdrawal bleeds were normal or scanty. Intermenstrual spotting occurred in 7.1% and break-through bleeding in 4.4% of all treatment cycles. The incidence of adverse events was similar to that of other gestagen-estrogen combinations. The results of the study demonstrate that Diane-35 provides an effective therapy for androgenized oligomenorrheic women with PCOS wishing simultaneous contraceptive protection.