A 23 year-old man with x-linked Becker type muscular distrophy underwent cardiac transplantation because of dilated cardiomyopathy complicated by terminal heart failure. The muscular functional impairment was mild and slowly progressive, whereas the cardiac disease was severe and rapidly progressive. The ventricular cavities of the explanted heart were hugely dilated and the left ventricular wall thickness was moderately increased. Microscopically, a diffuse hypertrophy of the myocardial fibers and a widespread interstitial collagenous fibrosis were present. At a follow-up, two years after treatment, the patient is alive and fairly well; the degree of his muscular disability is substantially unchanged.