Clinical and pathological abnormalities of the heart that may have major functional significance in those conditions were studied in collagen disease (total 242 cases). 1. atypical verrucous endocarditis (Libmann-Sacks) were found in 2 cases with loupus erythematosus (25 cases) and in 1 case with scleroderma (3 cases). 2. Rheumatoid nodules were not seen in the heart of rheumatoid arthritis patients (9 cases). 3. The most frequent findings in the heart with collagen diseases were pericarditis, fibrous scarring of the heart muscle, focal inflammation and vasculitis is similar to periarteritis nodosa or endoarteritis obliterans. 4. Morphological changes of the A-V node were found in patients who had A-V dissociation or A-V block before death. Heart muscle infarctions were found in 2 cases.