The concentrations of angiotensin I (AI) and II (All) were determined by radioimmunoassay in blood from the main pulmonary artery (MPA) and left ventricle (LV) often subjects with rheumatic valvular heart disease. The levels of AI were consistently higher in MPA plasma (21.8±2.4 pmol/1) than in LV plasma (14.7±2.0 pmol/1), paired t, P1]angiotensin II, [des-(Asp1 Arg2)]angiotensin II [des-(Asp2Arg2Val3)]angiotensin II. To characterize the nature of circulating All immunoreactive material, paper chromatography was used to separate All from its immunoreactive metabolites. The results showed that 84-100%of the All immunoreactive material from both MPA and LV plasma chromatographed with the mobility of authentic angiotensin II. The mean pulmonary conversion of endogenous AI was 33±4.8%and the net extraction of All by peripheral tissues was 33±4.1%.