A postmortem examination was performed on a male child who had lived to twelve months of age, at the Institute of Pathology of the Medical Faculty of Comenius University in Bratislava, Czechoslovakia. The clinical diagnosis had been mucoviscidosis, bronchopneumonia, and dystrophy. Findings characteristic of cystic pancreas fibrosis and bronchopneumonia of the right lower lung lobe were macroscopically recorded and were microscopically established. Massive fibrotic and necrotic lesions were primarily recorded from the left cardiac ventricle and were considered to be unusual findings. Damage to the myocardium is a very rare complication of mucoviscidosis. Less than 50 cases have so far been described, according to Benesová et al. (1983).