The authors report their experience with two-stage surgical treatment of severe ventricular septal defects in babies: initial banding of the pulmonary artery, followed by closure of the ventricular septal defect and removal of the band by an open-heart technique. Out of 162 operations to band the pulmonary artery, 90 were for cases of ventricular septal defect. The mortality was low (9.1%) when there was a ventricular septal defect with or without a patent ductus. It is considerably higher (31.4%) when there is a coincident coarctation of the aortic isthmus. So far 38 children have had the second operation, with 2 deaths. The authors have studied the surgical problems and the long-term results (6 months to 3 years follow-up) in the first 29 patients undergoing surgery. Although the results from this two-stage operation are good, when the authors take into account their current experience with one-stage closure of ventricular septal defects in the babies, they feel that this latter technique is to be preferred. Reservations must, however, be expressed when the child is very young (Weighing 3.5 kg or less), when there are multiple defects between the ventricles, and when the defect is severe, with a combination of VSD, patent ductus and coarctation of the aorta, and sometimes when the opertion must be carried out as an emergency.