Sixty-two Asian Indian and American vegetarians participated in a 3-h glucose tolerance test after an overnight fast to study clinical indices of glucose homeostasis. The Asian Indians had a higher (p less than 0.0035) insulinogenic score than the Americans. The Asian Indians had significantly higher insulin levels than the Americans at every sampling time during the glucose tolerance test except for the 3-h sample. The Indian men had significantly higher (p less than 0.05) plasma glucose than the other three groups at 2 h after the glucose load. American subjects had higher (p less than 0.0008) insulin binding to erythrocytes than the Asian Indian subjects. Scatchard analysis and competition-inhibition plots of the insulin-receptor data indicated that decreased binding in the Indian group results from a lowered number and decreased affinity of erythrocyte receptors. These results suggest that Asian Indians exhibit several clinical indications associated with an increased risk for the development of insulin-independent diabetes.