Strict vegetarians, who eat little if any animal products and lactovegetarians, who regularly eat dairy products, have lower blood pressures than the general population after adjustment for the effects of age, sex, and body weight. Controlled dietary trials were undertaken to determine the dietary basis for the differences in BP between vegetarians and nonvegetarians. Exchanging meat and eggs for vegetable products; increasing total dietary protein or replacing soy protein with dairy protein; exchanging saturated, monounsaturated, and polyunsaturated fatty acids; and changing the content of total dietary fat and carbohydrate all had no substantial effect on BP. Therefore, animal products, carbohydrate, and different types of fats do not appear to explain the low BP in vegetarians. Rather, modest intake of animal products may be a marker for a large intake of other potentially beneficial nutrients from vegetable products.