Increasing numbers of asymptomatic masses of the adrenal gland are being discovered by high resolution computed tomography (CT) scanning. The significance of these masses and the question of further evaluation or treatment, or both, have posed a dilemma. From 1976 to 1983, an incidental finding of adrenal gland mass was identified in 88 patients undergoing abdominal CT scanning for unrelated problems. Adrenelectomy was performed upon 23 patients (26 per cent), including three adenomas (2.5, 3.0 and 6.5 centimeters), five carcinomas of the adrenal gland (6 to 20 centimeters), two hyperplasias and three adenocarcinomas of unknown origin. Thirty-eight (43 per cent) of the nonfunctioning masses were observed with repeat scans for an average of 25.1 months (three to 60 months), revealing no change in size. Twenty-seven patients (31 per cent) were lost to follow-up study. Silent primary (nonmetastatic) masses 3.5 centimeters or less manifested benign behavior without exception. Based upon these data, we conclude that all solid metabolically inactive lesions in the adrenal glands greater than 3.5 centimeters on CT abdominal scan deserve exploration. Lesions less than 3.5 centimeters may be safely followed with serial CT scans.