To prepare a healthy patient for operation and to guide him through a speedy and successful convalescence is usually not difficult. However, when disease has caused important abnormal physiologic changes and when the necessary operative procedures are long and traumatic, the difference between a successful outcome and a failure will lie in the skill with which the patient is supervised before, during and after operation. The human body has remarkable powers of adaptation when all its systems are functioning, and it has rich reserves with which to compensate for deficiencies produced by disease and treatment. Many mistakes made in the past were those of well intentioned but unreasoned therapy such as enforced bed rest, excessive drugging and overzealous parenteral feeding. EVALUATION OF THE PATIENT The preoperative preparation of the patient begins at the moment of the initial examination. It consists of an accurate evaluation of the physical and mental status