1. Though the average blood sugar curve in 26 patients given a glucose tolerance test was within normal limits, only six of the individual curves were within normal limits.2. The blood sugar curve obtained in the insulin tolerance test in these 26 patients was characterized by a marked prolongation of the time required for a return to the fasting level.3. There was no correlation between the insulin and glucose tolerance tests and the average coma dose.4. The onset of coma was dependent not only on a significant fall in the blood sugar level, but also on the length of time the low level was maintained.