Forty-nine healthy women aged 20-35 years who had not been pregnant or using an oral contraceptive (OC) for the previous 3 months were randomized into two groups, one group taking an OC containing 75 micrograms gestodene (GTD) and 30 micrograms ethinyl estradiol (EE), and the other group using an OC with 150 micrograms desogestrel (DSG) and 30 micrograms EE. Fasting blood samples were taken before treatment, and after cycles 3 and 6, between the 18th and the 22nd day of the cycle. Blood lipoprotein lipid levels were measured. Serum total cholesterol did not change significantly in both groups. However, in the first three cycles, serum triglyceride increased by 46% and 40% and HDL-cholesterol by 14% and 8% in the GTD and DSG groups, respectively. The serum LDL level decreased by 6.2% and 11.8%, respectively. Between the third and sixth cycle, no further significant changes were observed, nor did these changes differ significantly between the two groups. In conclusion, both OC preparations exerted small and probably favorable effects on serum lipoprotein lipid levels.