One autopsy case who had an unusual clinical course of a diabetic ketoacidotic coma and died of free perforation at just the proximal portion of the non-specific ulcers of the small intestine following internal fistula causing tight adhesion of 3 intestinal loops is reported. This 55 year-old obese female patient had been well untill one month ago when she began to complain of thirst, anorexia, nausea, and recurrent vomiting. She fell into disturbance of conciousness in the morning on admission and was admitted in a preliminary diagnosis of impending diabetic coma. The patient soon recovered from diabetic ketoacidotic coma. Insulin dose was decreased gradually and the patient went into a good controlled state by diet therapy alone without insulin on the 54th day after admission. However, her abdominal distress persisted and upon examination of the abdomen, we found that the multiple intestinal ulcers had caused internal fistulas which created the adhesion of the intestinal loops. From a clinical standpoint, Crohn's disease could not be diagnosed and even histologically, there were no granulomes. Therefore, this lesion could be said to be non-specific ulcers of small intestine with fistula formation. We could not clarify the relationship between diabetic ketoacidotic coma and these rare intestinal lesion. By autosy, chronic pancreatitis was found. We believe that no relationship existed between the diabetic ketoacidotic coma and the chronic pancreatitis.