Cytopathologic smears and/or imprints of human adrenal cortex (9 cases) and its disorders were examined, including adrenocortical nodule (3 cases), adrenocortical adenoma (23 cases), carcinoma (8 cases), and renal cell carcinoma (6 cases). Immunocytochemistry directed against 3 beta-hydroxysteroid dehydrogenase and adrenal-4-binding protein (Ad4BP), a transcription factor in steroidogenesis, was also performed. There were no cytologic differences between normal adrenal and adrenocortical nodules. Large nuclei with prominent nucleoli were observed predominantly in adrenocortical neoplasms. Cellular atypia or pleomorphism and the degree of cohesiveness were unreliable criteria in differentiating between adrenocortical adenoma and carcinoma. Mitosis and necrotic materials were observed only in adrenocortical carcinoma. These cytologic findings were considered contributory, but not diagnostic when evaluating adrenocortical disorders because of marked intra-tumoral heterogeneity. There were no reliable cytologic criteria in differentiating adrenocortical and renal cell carcinoma. Immunocytochemistry of 3 beta-hydroxysteroid dehydrogenase and especially Ad4BP was demonstrated to aid greatly in the differential diagnosis between these carcinomas by identifying adrenocortical parenchymal cells.