The National Institutes of Health Consensus Development Program convened surgeons, endocrinologists, pathologists, biostatisticians, radiologists, oncologists, and other health care professionals, as well as members of the general public, to address the causes, prevalence, and natural history of clinically inapparent adrenal masses, or "incidentalomas"; the appropriate evaluation and treatment of such masses; and directions for future research. Improvements in abdominal imaging techniques have increased detection of adrenal incidentalomas, and because the prevalence of these masses increases with age, appropriate management of adrenal tumors will be a growing challenge in our aging society. To address six predetermined questions, the 12-member nonfederal, nonadvocate state-of-the-science panel heard presentations from 21 experts in adrenal incidentalomas and consulted a systematic review of medical literature on the topic provided by the Agency for Healthcare Research and Quality and an extensive bibliography developed by the National Library of Medicine. The panel recommended a 1-mg dexamethasone suppression test and measurement of plasma-free metanephrines for all patients with an adrenal incidentaloma; additional measurement of serum potassium and plasma aldosterone concentration-plasma renin activity ratio for patients with hypertension; and surgery for patients with biochemical evidence of pheochromocytoma, patients with tumors greater than 6 cm, and patients with tumors greater than 4 cm who also meet other criteria. The panel also advocated a multidisciplinary approach to managing adrenal incidentalomas. The statement is an independent report of the panel and is not a policy statement of the National Institutes of Health or the federal government.