We measured total, HDL and LDL cholesterol and triglycerides in 183 postmenopausal women before and 4 weeks after hormone therapy. Ethinyl estradiol or conjugated estrogens alone or in association with medroxyprogesterone, norethyndrone or norgestrel were used in different dosages either continuously or sequentially. Total cholesterol decreased from 206 to 196 mg/dl and HDL raised from 47 to 53 mg/dl (p less than 0.001) except in the group treated with estradiol-levonorgestrel in which HDL fell from 41 to 36 mg/dl (p less than 0.001). HDL cholesterol decreased from 133 to 113 mg/dl, overall. The total cholesterol/HDL ratio decreased from 4.8 to 4.2 in all groups except the group previously mentioned. Estrogen therapy, isolated or in association to medroxyprogesterone induced a moderate increase in serum triglyceride levels (132 to 149 mg/dl, p less than 0.001). Thus, the administration of estrogens in postmenopausal women is associated with a decrease in total, LDL and total/HDL cholesterol ratio and an increase in triglycerides. Norgestrel but not medroxyprogesterone partially revert these effects.