This report describes a retrospective study of 23 patients with incidentally discovered adrenal masses. Two patients with subclinical cortisol secretion developed adrenal insufficiency after removal of benign adenomas. Another patient, who probably harbors an asymptomatic pheochromocytoma, developed a hypertensive crisis when a mass was palpated during aortic vascular surgery. Twelve patients underwent surgery. Seven benign adenomas, an angiomyolipoma, and a cyst were removed. Three patients had malignant masses that include an angiosarcoma, an adrenal adenocarcinoma, and a congenital neuroblastoma. We conclude that hormones, especially cortisol, may be secreted in subclinical amounts by incidentally discovered masses. We recommend a concise laboratory evaluation that includes an overnight dexamethasone suppression test. Based on our interpretation of the literature, we believe masses greater than 3 cm in size should be removed. Patients who do not undergo surgery should have computed tomographic scans repeated for one year and should be reassessed periodically for the development of hormone secretion.