The most important preoperative procedure is to establish a firm diagnosis. Clinical findings often indicate the altered pathophysiology, but extensive endocrine studies are usually necessary, not only to establish the disorder within the adrenals but also to rule out associated disorders in other endocrine glands. Unless they are malignant, tumors are seldom large enough to be identified by pyelography, tomography, retroperitoneal gas injection, or aortography. Computed tomography scans may be helpful. Accordingly, the reader should refer to current texts on diagnostic endocrinology for the required procedures. When adrenalectomy is decided upon, the surgeon should investigate and, if possible, correct many of the secondary systemic and metabolic effects that are the direct result of the altered functional activity of the adrenal. The management of the hypertension and its cardiovascular sequelae is a major problem with pheochromocytomas. Problems associated with hypercorticolism include hypokalemia with alkalosis, hypertension, polycythemia, musculoskeletal depletion with osteoporosis and hypercalcemia, abnormal glucose tolerance, multiple areas of skin furunculosis, and, finally, poor wound healing. Thus, the surgeon must be aware that many organ systems and their responses to surgery are profoundly affected by adrenal malfunction.