We have studied the effects of dextrose, rice, potato, corn, and bread on postprandial plasma glucose and insulin responses in 16 subjects. All carbohydrate loads were calculated to contain 50 gm. of glucose. The data demonstrate (1) that dextrose and potato elicited similar plasma glucose responses whereas rice, corn, and bread elicited lower responses; (2) similarly, dextrose and potato elicited similar and greater plasma insulin responses than rice and corn, with the response to bread being intermediate; (3) when the study group was divided in half, on the basis of each subject's one-hour plasma glucose response to dextrose, the differences in the plasma glucose and insulin responses were greater in the subjects with the highest glucose response to dextrose than in the low responders. In conclusion, there is a range of plasma-glucose and insulin responses to different complex carbohydrates, with rice and corn producing the lowest response curves. Furthermore, these differences are accentuated in patients with reduced glucose tolerance.