In general, vegetarians have lower serum lipids and blood pressures than omnivores have. We tested the blood pressure and serum lipid lowering effects of two fat-modified diets differing primarily in their source of protein. Twenty-six men were randomized in an incomplete block design to two of three diets: a high-fat diet, a fat-modified lactoovovegetarian diet (LOV) and a diet in which 60% of plant protein in the LOV was replaced with lean meat (LM). Compared with the high-fat diet both prudent diets significantly lowered blood pressure, serum total cholesterol (TC), and LDL cholesterol but significantly increased serum triglycerides. The LOV diet had a significantly greater cholesterol-lowering effect than did the LM diet (10% vs 5% decrease) but blood pressure reductions were similar. The partial substitution of lean meat for plant protein in a fat-modified diet did not negate the overall cardiovascular-risk lowering of the lactoovovegetarian diet.