Severe abdominal pain and tenderness occured in 46 of 211 episodes of severe diabetic metabolic decompensation. No association was found between abdominal pain and the degree of dehydration or the initial blood glucose level. In 17 instances, the abdominal pain could be attributed to the precipitating cause of the metabolic decompensation. The episodes of unexplained pain all occurred insulin-dependent patients less than 40 years of age; of these, only three had a plasma bicarbonate level greater than 10 mEq/liter, and in two patients, additional factors could account for the relative lack of ketoacidosis. Abdominal pain occurring in patients more than 40 years old, irrespective of the plasma bicarbonate level, and in patients of any age with a plasma bicarbonate level in excess of 10 mEq/liter, almost invariably indicates a specific underlying cause.