The perioperative management of diabetic patients implies glicemic normalization before, during and after the procedure. Insulin therapy is always necessary when general anesthesia is considered, and in most cases of epidural analgesia. When ambulatory surgery is envisaged, the usual hypoglycemic treatment can be maintained, provided that a sufficiently good metabolic control is documented. The pathophysiological mechanisms for insulin-resistance in these situations are reviewed, as are the procedures for general clinical evaluation of the patient. The estimation of insulin needs, the problems related with the suspension of oral antidiabetic drugs and the description of the most usual schemes of intensive insulin therapy (namely those of continuous intravenous insulin infusion) are also detailed.