Factors controlling proliferation of adrenocortical cells have been studied in Although several purified polypeptides have been reported to stimulate the proliferation of animal cells-in culture, a high degree of cell specificity has not been observed. Fibroblast growth factor (FGF) is mitogenic for fibroblast, adrenocortical, myoblast, smooth muscle, chondrocyte, vascular endothelial, granulosa, and luteal cells, whereas epidermal growth factor (EGF) is mitogenic for fibroblast, corneal epithelial, certain mammary epithelial, and granulosa cells (1). Several pituitary polypeptides long considered trophic for specific target cells in ivo either inhibit DNA synthesis when added directly to target cells in culture or have no effect on growth (2-6). Understanding of the mechanisms controlling organ-specific growth is, therefore, incomplete; interaction of several growth factors and hormones may be involved (7).A recently developed strain of bovine adrenocortical cells in culture has been used to study factors controlling proliferation of the adrenal cortical cell (8). FGF but not EGF stimulates proliferation of these cells, whereas corticotropin (ACTH) and prostaglandin El (PGE1), which stimulate cyclic AMP formation, inhibit proliferation (8, 9). Corticotropin and PGE1 both stimulate steroidogenesis and induce the steroid biosynthetic pathway. The present studies indicate that angiotensin II and III at low concentrations stimulate DNA synthesis as well as steroidogenesis in adrenocortical cells. The growth-stimulatory effect of angiotensin appears specific because several cell types, including cells reported to possess angiotensin II receptors, do not increase DNA synthesis with addition of angiotensin II (Schwarz/Mann) was routinely added to cultures 12 hr after addition of growth stimuli. Twelve hours later, medium was removed and 1 ml of a 1% aqueous solution of Triton X-100 was added. The cells were incubated with this solution for 5 min and the entire contents of the plate