The Multiple Risk Factor Intervention Trial was a randomized clinical trial that studied the efficacy of multiple risk factor reduction in lowering coronary heart disease mortality in high-risk men. Nutrition counseling based on a fat-modified eating pattern resulted in a significant reduction of total cholesterol and low-density lipoprotein cholesterol. However, based on further analysis not involving comparisons of randomized groups, the reduction in total cholesterol appeared to be blunted by the effects of the antihypertensive medication utilized in the stepped-care therapy in this study. The use of diuretics was associated with an increase in triglycerides and a lesser decrease in total plasma cholesterol when compared with non-diuretic users. The use of diuretic therapy was also associated with a slight decrease in high-density lipoprotein cholesterol, when compared with changes in those not receiving diuretic therapy. The combination of diuretics plus propranolol was related to a substantial decrease in high-density lipoprotein cholesterol in both the Special Intervention and Usual Care participants. The changes in lipoproteins for men receiving diuretic therapy are probably influenced substantially by nutritional factors, especially weight change. Concomitant nutritional changes must be considered when analyzing the short- and long-term effects of therapy with diuretics or other antihypertensive drugs on lipoprotein metabolism.