A review was made of 69 cases manifesting congestive right-side heart failure among 1, 910 cases who had undergone cardiac catheterization at the Department of Pediatrics, Tenri Hospital. Hemodynamic and angiographic studies were made in 32 cases which had undergone corrective surgery of tetralogy of Fallot at ages between l to 14 more than 2 years earlier. The circulatory responses to exercise were also studied in 21 patients to evaluate the pumping performance of the heart. Although all patients but 2 with operatively corrected tetralogy of Follot are quite asymptomatic, there were elevations of RVEDP noted despite the absence significant residual pulmonary stenosis at rest. In addition, patients revealed abnormal hemodynamic response to exercise. It was also noted that among patients with residual pulmonary stenosis a large systolic pressure gradient across the right ventricular outflow tract appeared during exercise. In addition to the evaluation of residual pulmonary stenosis by routine catheterization, the clinical importance of the evaluation of right ventricular performance in response to exercise following operative correction of tetralogy of Fallot was identified as an essential feature in long-term medical management.