Cultured bovine aortic endothelial cells (BAEC) contain renin and angiotensinogen. To examine whether angiotensins are synthesized intracellularly and secreted by these cells, we assayed cell extracts as well as serum-free media of intact confluent BAEC. Angiotensins were identified by their retention time on reverse phase high performance liquid chromatography and direct radioimmunoas-say. BAEC and their media contain angiotensin II and angiotensin III. The rate of angiotensin accumulation in the media was a nonlinear function of time; the highest rate occurred in the first 15 minutes. The amount of angiotensin II accumulated in 30 minutes exceeded 200% of the intracellular concentration and that of angiotensin III exceeded 500% of the initial intracellular content. Neither renin nor angiotensinogen could be detected in the media. The viability of these cells was supported by low lactic dehydrogenase activity in the media (<0.5% of cellular level). These data suggest that BAEC is capable of synthesizing and secreting angiotensins. We postulate tht this endothelial-derived angiotensin system may play an important paracrine or autocrine role in influencing local vascular tone.