Increasing evidence indicates that angiotensin II can be formed by juxtaglomerular cells (JGC) and cosecreted with renin. We investigated the existence of this local renin-angiotensin system in a human JGC tumor, using an in vitro superfusion. The JGC tumor was found concomitantly to release renin and angiotensin I and II. Sequential addition of atrial natriuretic peptide, dopamine, and a somatostatin analog in the superfusion did not affect renin or angiotensin I and II release. The data provide evidence that the human JGC tumor in vitro generates angiotensin II, and supports its possible role as a local in vivo regulator of kidney function.