Two triphasic oral contraceptives containing the same amount of ethinyl estradiol in combination with gestodene or levonorgestrel were compared with respect to contraceptive effect, cycle control, and effects on lipid metabolism and coagulation. Serum concentrations of gestodene, levonorgestrel, ovarian and pituitary hormones, and sex hormone-binding globulin were measured. Thirty-three healthy women were randomized into two groups receiving either of the preparations. Before treatment and in the third and sixth cycles, blood sample were drawn in the morning while subjects were still in bed to obtain basal conditions. The contraceptive effect and cycle control were good with both preparations, and there were only a few minor side effects. Sex hormone-binding globulin was elevated twofold in the levonorgestrel group and threefold in the gestodene group. The gestodene concentration in serum varied more than the levonorgestrel concentration, but with correction for variations in sex hormone-binding globulin binding, less variability in gestodene and levonorgestrel concentrations were seen. High-density lipoprotein₂ cholesterol decreased in the levonorgestrel group but was unchanged in the gestodene group, whereas apolipoprotein A₁ increased in the gestodene group but not in the levonorgestrel group. Antithrombin III decreased in the gestodene group but was unchanged in levonorgestrel-treated women. Factor VII increased in both groups but more in the gestodene group. We conclude that gestodene has a positive influence on lipid metabolism, probably because of its lower androgenicity, and a slightly negative influence on coagultion. The latter, however, probably has no clinical relevance.