Surgical banding of the pulmonary artery in patients with transposition of the great arteries leads to a rapid increase of the left ventricular mass. The purpose of this animal experiment was to induce ventricular systolic hypertension in the “subpulmonary ventriclerdquo; by intravascular obstruction to pulmonary flow. The first experiment was performed in an anesthetized animal with an open thorax. A balloon-tipped catheter was introduced into the femoral vein and advanced to the pulmonary artery. The balloon was positioned in the pulmonary trunk and was progressively inflated until a systemic pressure was achieved in the “pulmonary ventricle”. This was accomplished within 40 minutes without a significant reduction in cardiac output, which was continuously monitored by an electromagnetic flowprobe. In the second experiment an analogous procedure was performed in a closed chest, awake, spontaneously breathing animal. The catheter was maintained in proper place for 24 hours. Subsequent macroscopic examination of the heart demonstrated a remarkable increase in the ventricular mass. The results of this preliminary experiment demonstrate the possibility for creating “intraluminal pulmonary banding”. The potential advantages of this technique are the nonsurgical approach and the ability to adjust the grade of obstruction to pulmonary flow.