We have studied the acute effects of oral ingestion of dextrose, rice, potato, corn, and bread on postprandial serum glucose, insulin, and glucagon responses in 20 diabetic subjects with nonketotic, noninsulin requiring fasting hyperglycemia. The carbohydrate loads were all calculated to contain 50 g of glucose. The data demonstrate that 1) dextrose and potato elicited similar postprandial serum glucose responses whereas rice and corn elicited lower responses, with bread intermediate; 2) postprandial insulin responses were relatively flat but rice ingestion led to significantly lower insulin responses than did potato; 3) urinary glucose excretion during the 3 h after carbohydrate ingestion was greatest following dextrose and least after rice and corn. In conclusion, there is a range in the magnitude of postprandial hyperglycemia after ingestion of different complex carbohydrates in diabetic patients with fasting hyperglycemia and emphasis on the use of the less hyperglycemic starches could be of therapeutic value in controlling hyperglycemia.