Over the years 1971 to 1988 autopsies of 33 children with the clinical diagnosis of mucoviscidosis were performed at the Institute of Pathology, Medical Faculty, Comenius University, Bratislava. In three cases pronounced changes were observed on the myocardium, predominantly on the left ventricle. Multifocal necrosis and fibrosis of the myocardium represent rare but severe changes occurring as a complication of mucoviscidosis in infancy.