Cortisol, corticosterone, epinephrine and norepinephrine have been identified for the first time in two adrenal cysts removed from patients without endocrine dysfunction. Total concentrations of corticosteroids and catecholamines in both capsule and fluid of these cysts were higher than in plasma of normal subjects but lower than in human adrenal tissue. The cysts contained preformed cholesterol in concentrations similar to normal adrenal parenchyma. Contrary to adrenal tissue, however, homogenates of cyst components failed to utilize [4-14C] cholesterol for steroid formation. The data presented suggest that hormones in adrenal cysts probably arise by passive diffusion from the surrounding gland and that the endocrine status of patients bearing adrenal cysts is determined by the adjacent non-cystic tissue.