DCRV is a rare cause of right ventricular outflow obstruction by anomalous muscle bundle at the level of sinus portion. The symptoms due to DCRV itself were mild inspite of significant pressure gradient over 90mmHg between proximal and distal chamber, and became severe by associated complication of bacterial endocarditis or aortic regurgitation in ventricular septal defect. In 12 cases(40%), right ventricular hypertrophy configuration in electrocardiogram was characteristic. Although R wave in V1 was tall, S wave in V6 and R wave in aVR were indistinctive. Those were very useful findings for diagnosis of DCRV which was thought to be possible only invasively. With operation prior to overt right ventricular faliure, the prognosis was good with only minor complication.