This study was undertaken to characterize the clinical pictures of long-standing overload of the right ventricle and to investigate its hemodynamics. 1. Myocardial cell injury of the right ventricle was studied. Histopathological examinations were performed by biopsy in patients with atrial septal defect (ASD). Cell diameter was more widely distributed in the disease compared to the control. The range of distribution was more markedly scattered in ASD with congestive heart failure. Change in the ultra-fine structure was also more remarkable in ASD with than without pump failure. 2. ASD with impending myocardial infarction was discussed as an example of associated acquired disease. 3. The occurrence of pulmonary hypertension could be monitored with recently developed color Doppler method. A representative case of ASD and pulmonary hypertension was presented and discussed. 4. Right ventricular overloading associated with arrhythmias was presented. The effects of arrhythmias on Ebstein's anomaly and Uhl disease were examined. In these anomalies, development of pump failure and life-threatening arrhythmias were serious problems in managing old patients. In summary, histo-pathological examinations, monitoring of pulmonary artery pressure by Doppler echocardiography and management of arrhythmias were necessary to evaluate prognosis of congenital heart disease in the elderly.