• The antidiabetic effects of carbutamide and tolbutamide were studied in 11 normal and 7 diabetic subjects. Doses of 2 gm. of either drug given by mouth under certain standard conditions produced a lowering of the blood sugar level in 10 of the normal subjects. Case histories of the diabetic subjects here given show that only one had a prompt and completely satisfactory response; another had a delayed but ultimately satisfactory response. The responses of the remaining patients were unsatisfactory, and in two the drugs were entirely ineffective. Mild, transient leukopenia was observed twice. Since five of the diabetic subjects had been selected as suitable candidates for sulfonylurea therapy on the basis of previous reports, it appears that the indications and limitations of these drugs require further study.