A comparison was made between the glycemic and glycosuric responses after ingestion of equivalcnt amounts of glucose derived from glucose per se, protein, and carbohydrate foods in normal men and in diabetic patients. In both groups the resulting hyper-glycemia was much greater after carbohydrate than after protein ingestion. In the diabetics a significant gly-cosuria resulted from carbohydrate feeding; little or none occurred when the glucose was derived from ingested protein. The slow and prolonged liberation of glucose into the blood stream during protein metabolism enables the diabetic to utilize a greater total amount of glucose per unit of time without glycosuria than is possible when carbohydrate foods are fed.