Congestive cardiomyopathy was diagnosed during post mortem examination in eight of 149 adult woodchucks from New York. The eight woodchucks, four males and four females, died spontaneously without clinical signs of heart failure having been detected. The primary lesion was a grossly enlarged and dilated heart. Histologic lesions consisted of multifocal myocardial degeneration and necrosis. Secondary lesions of congestive heart failure were observed.