With RIA/HPLC and immunohistochemistry, the presence of angiotensin(A) and atrial natriuretic factor-like materials (ANF-LMs) was demonstrated in the pericardium of human and rats; the distributions of AII and ANF-LMs were found to be identical; AI was more than AII; renin activity was detected in the pericardium. There were three molecular forms of ANF-LMs in the pericardium. Mesothelial cells were the principal endocrine-secreting cells. AII and ANF-LMs of the pericardium were significantly increased in rheumatic heart disease. There were no correlations between plasma AII, ANF, urine AII, ANF and pericardial AII, ANF (P > 0.05). The data reported showed that the pericardium may have endocrine function under normal and abnormal conditions (heart failure) of the heart, in addition to its known mechanical properties.