Vegetarians have relatively low blood pressure (BP) levels and consume less protein than do nonvegetarians , and there have been suggestions that certain proteins may raise BP. To determine whether dietary protein supplements raise the BP of vegetarians, 58 g/per day of a 60:40 mixture of soy and wheat proteins and an isocaloric low protein supplement supplying 7 g/day of rice protein were added for 6-week periods to the diet of 18 vegetarians in a 2-group crossover design. Mean daily protein intake during consumption of the low and high protein supplements was 63 and 119 g, respectively. Mean BP was 109/72 mm Hg after the high protein and 108/71 mm Hg after the low protein diet. Consumption of other major nutrients, mean body weight, and sodium and potassium excretion did not change significantly. Thus, protein supplementation of a vegetarian diet that contained a below average but nutritionally adequate amount of protein did not significantly affect BP over 6 weeks.