This randomized, double-blind study was undertaken to compare the efficacy and tolerability of policosanol (10 mg/day) and lovastatin (20 mg/day) in patients with hypercholesterolemia and noninsulin dependent diabetes mellitus. After 6 weeks on a lipid lowering diet, 53 patients were randomized to receive either policosanol or lovastatin tablets that were taken o.i.d. for 12 weeks under double-blind conditions. Both groups were similar at randomization. Policosanol significantly (p < 0.001) lowered low-density lipoprotein (LDL)-cholesterol (20.4%), total cholesterol (14.2%) and the ratio of LDL-cholesterol to high-density lipoprotein (HDL)-cholesterol (23.7%). Lovastatin significantly (p < 0.01) lowered LDL-cholesterol (16.8%), total cholesterol (14.0%) and the ratio (p < 0.05) of LDL-cholesterol to HDL-cholesterol (14.9%). Triglyceride levels did not significantly change after therapy. Policosanol, but not lovastatin, significantly increased (p < 0.01) levels of HDL-cholesterol (7.5%). Comparison between groups showed that changes in HDL-cholesterol induced by policosanol were significantly greater (p < 0.01) than those induced by lovastatin. Both treatments were safe and well tolerated. Lovastatin moderately but significantly (p < 0.05) increased levels of aspartate aminotransferase, creatine phosphokinase and alkaline phosphatase. Adverse reactions were more frequent in the lovastatin group (p < 0.01) than in the policosanol group. In conclusion, policosanol administered at 10 mg/day produces more advantageous changes in HDL-cholesterol and has a better safety and tolerability profile than lovastatin 20 mg/day.