Confirmation and clinical application is reported of Somogyi''s findings that hypoglycemia, whether spontaneous or induced by insulin, causes ketosis. Four cases are described in 3 of which excessive insulin dosage was responsible for ketonuria. When the amt. of the insulin was reduced or completely eliminated to avoid hypoglycemia, ketonuria was checked. The interpretationof this phenomenon has been discussed and its importance with reference to the management of diabetic patients has been pointed out.