In the present study the effects of a combined oral contraceptive preparation containing 0.150 mg desogestrel and 0.030 mg ethinylestradiol on lipid metabolism were investigated. In particular, we observed significant increase in HDL-cholesterol and apolipoprotein-A-I (apo A-I) and B (apo B). Triglycerides were not significantly modified. The cholesterol esterifying enzyme LCAT, assayed under "maximal" conditions against an exogenous substrate, was significantly decreased despite an increase in the physiological stimulator apo A-I. No changes were observed in the anti-atherogenic indexes apo A-I/apo B and HDL-cholesterol/LDL-cholesterol. Thus, it appears that this combined oral contraceptive has the promising ability to increase the anti-atherogenic HDL-cholesterol particle without altering the atherogenic LDL-cholesterol.