We report a case of traumatic rupture of the chordae tendineae of the tricuspid valve with a congenital left pleuro-pericardial defect. The chest X ray film revealed a large cardiac silhouette which protruded to the left. Echocardiographic findings were: 1) large right ventricle and paradoxical septal motion 2) tricuspid regurgitatin which was recognized by contrast echocardiography 3) small left ventricle. This case also had a characteristic finding of systolic fine oscillation on the posterior tricuspid leaflet. Computed tomograms explained the discrepancy (protrusion to the left in chest X ray and small left ventricle): Computed tomograms of the heart revealed an enlarged right atrium and right ventricle associated with prominent clockwise rotation of the heart. Open heart surgery, performed successfully 16 years after the non-penetrating trauma, revealed the congenital pericardial defect which produced the findings of computed tomogram.