Problems of diagnosis and treatment were analyzed in 27 patients with Cushing syndrome (25 confirmed by anatomic findings) followed for a mean of 50 months. The etiology was Cushing disease in 14 (52%), suprarenal tumor in 9 (33%) and ectopic secretion of ACTH in 4 (15%). Determination of plasma cortisol levels at 4 PM or 11 PM was a highly sensitive test for the presence of this syndrome (100%). High resolution computed tomography was considerably more effective than conventional X ray studies of the sella in patients with Cushing disease (42 vs 20%). Treatment has been totally effective in all patients with benign suprarenal lesions. Cure was obtained in 64% of patients with pituitary lesions and 0% of patients with Cushing syndrome associated to malignancy.