The effects of stanozolol, 17-methyl-2H-5α-androst-2-eno[3,2- c ]pyrazol-17β-ol, on lipoprotein levels were assessed in a short-term (6 wk) prospective study of 10 normolipidemic, postmenopausal, osteoporotic women. While total cholesterol and triglyceride levels remained constant, equal and offsetting responses were seen in low density lipoprotein (LDL) cholesterol (+ ± mg/dl [mean ± .], p < , a 21% increase) and high density lipoprotein (HDL) cholesterol (− ± mg/dl [mean ± .], p < , a 53% decline). Hence the LDL HDL ratio increased dramatically, from ± to ± . Within HDL, stanozolol was associated with a greater decline in HDL 2 (from ± mg/dl to ± mg/dl, p < , an 85% decrease) than HDL 2 (which diminished from ± to ± mg/dl, p < , a 35% decrease). The major HDL apolipoproteins also declined (A-I by a mean of 41% and A-II by 24%, both p < ). Postheparin hepatic triglyceride lipase increased (off treatment 74 ± 42 nmole free fatty acid min −1 mole −1 , on treatment 242 ± 110, n = 6, p = ). All changes were reversed by 5 wk following termination of the drug. These lipoprotein changes suggest caution in the long term prescription of stanozolol, particularly in those without overriding clinical indications for its use.