The cases of five patients with previous Senning (n = 4) or Mustard (n = 1) operations and failing systemic ventricles in whom banding of the pulmonary artery was performed as an interim step toward an arterial switch procedure are reported. The rise in the ratio of left to right mean systolic ventricular pressure, from 0.35 before operation to 0.90 during operation and 0.80 on the first postoperative day, caused a shift of the ventricular septum from a leftward to a midline or nearly midline position. This shift was associated with a reduction of tricuspid regurgitation. At a median interval of 5.1 months after pulmonary artery banding, the mean left ventricular posterior wall thickness had increased to 8.2 mm, versus 5 mm before operation, and the mean left ventricular myocardial mass index had increased to 90 gm/m2, versus 55.6 gm/m2 before operation. After the arterial switch operation, which was performed in four patients, the tricuspid regurgitation decreased to a trivial amount (n = 1) or disappeared completely (n = 3).