This study compared lovastatin and gemfibrozil therapy for effects on lipid and lipoprotein levels in 22 normolipidemic patients with reduced high-density lipoprotein cholesterol levels. Most patients had coronary heart disease. A randomized, crossover design consisted of two drug phases (lovastatin and gemfibrozil) alternating with placebo. Lovastatin reduced total and low-density lipoprotein cholesterol and apolipoprotein B levels by 28%, 34%, and 24%, respectively. These were unaffected by gemfibrozil. Both drugs reduced very low-density lipoprotein and intermediate-density lipoprotein cholesterol levels by 30% to 40%. Both caused small but significant increases in high-density lipoprotein cholesterol, but not in apolipoproteins A-I or A-II. Both significantly lowered ratios of total (and low-density lipoprotein) cholesterol-to-high-density lipoprotein cholesterol, but lovastatin more than gemfibrozil. Thus, for normolipidemic patients with low levels of high-density lipoprotein cholesterol, neither drug markedly raised high-density lipoprotein levels, but lovastatin produced the better overall change in lipoprotein cholesterol and apolipoprotein B levels.