The pathogenesis and treatment of diabetic ketoacidosis has been discussed. Insulin deficiency leads to increased rates of hepatic ketogenesis and gluconeogenesis with resultant hyperglycemia and ketonemia. Treatment consists of insulin and fluid replacement. Insulin therapy is titrated against the change in blood glucose concentration. Isotonic saline is the initial replacement fluid, and potassium is administered as required. Bicarbonate is employed in extreme acidosis, but its administration may contribute to the development of hypokalemia, CSF acidosis, and tissue hypoxia. It is hoped that a better understanding of the biochemical basis of ketoacidosis will permit the physician to develop a rational therapeutic regimen which will decrease the mortality associated with this condition.