Forty eight cases with infections endocarditis (IE) are analyzed--27 males and 21 females (75% at the age of 31-60). Only in 12.5% IE has developed on intact valvular apparatus. In 83.4% the preceding valvular pathology is rheumatic heart defect (RHD), and congenital cardiac malformations and valvular dysplasia--8.3% each. The mitral-aortic valvular defects predominate in RHD, followed by aortic, tricuspid and mitral ones. In 83.3% X IE is with valvular localization, in 4.2%--parietal and in 12.5%--on valvular prostheses. Vegetations are highly specific for valvular IE (100%) as well as ulcerations (90%) and perforations (45%). Ruptures of extra-valvular structures are established in 8.3%. The inflammatory alterations in myocardium are in 62.5%. The pericardial changes are found in 14.6%, mainly in the cases with valvular prosthesis. Septic changes are established in all cases in the spleen and regeneration of bone marrow, and vascular changes--in 85.4%. The cases with embolism and infarctions predominate in the kidneys (79.1%), followed by the cases with Löhlein's focal nephritis (18.6%). The inflammatory changes in liver are rare--6.9%. In 37.5% changes in brain were established, embolism according to incidence being first, followed by cerebral hemorrhages, cerebral abscesses and purulent leptomeningitis Staphylococcus aureus proved to be most frequent causative infectious agent established et necropsy.