Antibodies (Ab) reacting with the myocardial sarcolemma (SL) and interstitial connective tissue (ICT) were determined in 1333 rheumatic disease (RD) patients and in 286 healthy subjects of various age using indirect immunofluorescence technique. The age-related levels of SL and ICT Ab are responsible for the heterogeneous immune response to SL and ICT antigens. The presence of SL Ab is characteristic for young patients, of ICT Ab, for older patients. Children are found to have ICT Ab more infrequently, Sl Ab are more common in rheumatism than in other rheumatic diseases. The higher inflammatory process activity is associated with a more frequent presence of SL Ab and rare ICT Ab in each age group. In RD patients, SL Ab are considered to be risk factor of cardiac disease development. The ICT antigen is found to incorporate alpha-galactose. The reasons for the absence of ICT Ab in the healthy young and in patients with maximum inflammation are discussed.