Obstruction of the right ventricular outflow tract occurs in many various positions. Recently, obstruction due to anomalous muscle bundle has been clearly recognized. This anomaly is caused by a large anomalous muscle bundle, which creates an obstruction low in the body of the right ventricle and divides it into two chambers. Three cases of double chambered right ventricle were treated surgically utilizing cardiopulmonary bypass in the Department of Chest Surgery, College of Medicine, Seoul National University. 1] All of the 3 cases were female. 2] In 2 cases, FKG findings were RVH and RAD, but in case 2, normal EKG findings. 3] In case 2, no pressure gradient between the inflow portion and outflow portion of the right ventricle was observed, but in case 1 and 3, pressure gradients were 70 and 64 mmHg, respectively. 4] In 2 of the 3 cases, type II VSD was combined to double chambered right ventricle. 5] All of the 3 cases were discharged with symptomatic improvement after operation.[KTCS 1979;3:269-273]