An adrenal mass may be discovered incidentally in as many as 2% of patients having an abdominal CT scan. The clinical dilemma is to identify the rare functioning or malignant adrenal tumor, which warrants resection, while avoiding unnecessary testing and surgery in the majority of patients whose adrenal lesions are nonfunctioning and benign. A thorough history and physical examination and judicious use of screening laboratory tests are important in determining the likelihood of a clinically significant adrenal mass. There is little debate that functional or large (< 6 cm) adrenal masses should be excised; adrenalectomy for adrenal masses 3 to 6 cm in patients younger than 50 years of age and for those masses with ominous CT characteristics also is advised. Observation with serial CT scans and screening studies are recommended for patients 50 years of age or older whose adrenal masses are between 3 to 6 cm and for all patients with hormonally inactive masses that are smaller than 3 cm.