Bilateral testicular Leydig cell tumors in a patient with Nelson's syndrome and a Leydig cell tumor of the ovary in a woman with a virilizing syndrome were successfully imaged with [6beta-131I]iodomethyl-19-norcholest-5(10)-en-3beta-ol (NP-59). Uptake by these tumors was comparable to uptake by adrenal glands in patients with funtioning adrenal tumors or bilateral hyperplasia. Scanning the gonads with NP-59 may be a helpful imaging procedure in localizing possible sites for exploratory surgery in certain cases of gonadal neoplasia.