In the present study we measured the postprandial glucose, insulin, and gastric inhibitory polypeptide responses to 75 g carbohydrate administered either as glucose, unpolished (brown) rice, or ground brown rice to six recently diagnosed type 2 diabetics and six healthy subjects. The diabetic and normal subjects responded in a qualitatively similar manner to the three meals although there were major quantitative differences. Brown rice elicited significantly lower postprandial glucose, insulin, and gastric inhibitory polypeptide responses than either ground brown rice or glucose in both groups. There were no significant differences in the metabolic responses to ground brown rice (complex carbohydrate) and glucose (simple carbohydrate) in either diabetic or normal subjects. These data highlight the role of the physical form of complex carbohydrate in determining metabolic responses to it in both diabetic and normal subjects, and provide a rationale for designing diabetic diets containing complex carbohydrate in a form which is slowly digested and absorbed.