1. The effects of angiotensin I (AI) and angiotensin II (AII) have been compared during local infusions into peripheral arteries and veins in man.
2. Both AI and AII produced constriction of hand veins and forearm arteries; the potency of AI was somewhat less than AII.
3. When infused into the vein, the converting enzyme inhibitor SQ 20,881 abolished or markedly attenuated the effect of AI but not that of AII.
4. The results suggest the local presence of converting enzyme in human peripheral arteries and veins.