Twenty-one patients in severe diabetic coma were treated with small doses of insulin at a rate of 4.1 units per hour (total dose about 100 units per 24 hours). Using single doses of 4 to 10 units by the intravenous or intramuscular routes the fall of blood glucose was steady in all cases. In the treatment of diabetic coma this regimen of insulin administration has proved simple, safe and effective since 1946. Main dangers during recompensation of diabetic coma are: hypovolaemia with oliguria -- anuria, dysequilibrium syndrome with cerebral edema and hypokalaemia. Therefore early intensive and adequate intravenous fluid and electrolyte replacement is the most important part of treatment. Most of the cases in this study were undiagnosed diabetics (14) and elderly patients (9). Three patients older than 65 years and a 56-year old diabetic died. In this context the most important aspects of treatment to avoid death are: prevention of diabetic coma and adequate fluid and electrolyte replacement especially in geriatric patients.