The presence of angiotensin II-like substance (LATII-LS) in the human leucocytes was identified by means of immunofluorescence technique. And the LATII-LS PURIFIED purified by high-power liquid chromatography (HPLC). The effect of LATII-LS on isolated rabbit carotid arteries showed a definite vasoconstrictive character. It was surmised that this would play a role in causing the cerebral vasospasm after spontaneous subarachnoid hemorrhage.