Adrenal scans were obtained in 50 patients with suspected adrenal disease; 131I-19-iodocholesterol was used in 12 and 131I-6-beta-iodomethyl cholesterol (NP-59) in 38 cases (42 scans). The scan diagnosis was correct in 48 patients. Successful images were obtained with 0.5 mCi, or less, of NP-59 instead of the standard dose of 2 mCi, thus reducing radiation dose to the patient and cost of the agent. Satisfactory scans were obtained in 2--3 days in patients with hyperfunctioning adrenals, and in 3--7 days in other groups of patients, when NP-59 was used. With 131I-19-iodocholesterol, however, 5--10 days were required for optimal results in all patients including those with Cushing disease. Adrenal uptake studies were very useful in the evaluation of adrenal function, particularly in differentiating bilateral hyperplasia from normal adrenals.