Two patients with double inlet left ventricles were successfully treated by ventricular septation. Patient 1, a 38-year-old woman, underwent operation in 1971. This patient has been a full-time worker. Patient 2, a 2-year-old boy, had a relatively small left ventricle with an estimated volume of 134% of normal value. This patient underwent ventricular septation in 1995. He is now in New York Heart Association class II and enjoying school life.