This paper discusses the application of CT, MR imaging, and 131I-6 beta-iodomethyl-19-norcholesterol scintigraphy in establishing the nature of incidentally discovered adrenal masses. It is concluded that CT and MR imaging can permit confident differentiation between nonhyperfunctioning adenomas and metastases in cases of incidentalomas that meet all the criteria of a nonhyperfunctioning adenoma. In cancer patients, fine-needle aspiration biopsy of lesions is, in general, essential because a definitive diagnosis of metastatic disease is crucial to disease management. MR imaging and norcholesterol scintigraphy are useful if a relative contraindication for fine-needle biopsy exists or when biopsy results are inconclusive in patients with a presumably benign lesion.