For patients without a history of malignancy, most small (less than 3 cm) incidentally discovered adrenal masses are benign, and extensive and costly workup is usually not justified. For incidentalomas from 3 to 5 cm in size, computed tomography, magnetic resonance imaging, 2-[(18)F]fluoro-2-deoxyglucose positron emission tomography, adrenal biopsy, or surgery can be considered. Lesions larger than 5 cm should be removed because of the higher risk for malignancy. For patients with histories of malignancy, incidentally discovered adrenal masses are more often malignant, and thus even smaller adrenal lesions are suspect. Adrenal biopsy should be reserved for cases in which the results of noninvasive techniques are equivocal.