In November 1946, Potts, Smith and Gibson1reported a new surgical procedure for the relief of congenital pulmonary stenosis. The operation consists of a direct anastomosis between the aorta and a pulmonary artery. The use of the aorta was made possible by the invention of a clamp which permits blood to flow through this vessel while the anastomosis is being performed. This technic differs from the Blalock and Taussig2method only in the fact that the aorta itself rather than one of its branches is used to direct additional blood to the lungs. Anastomosis between the aorta and a pulmonary artery has been performed on 45 patients, and in addition 7 patients have been explored in whom the anastomosis was not undertaken. We shall first discuss the criteria used in the selection of these patients for operation.3 DIAGNOSIS In 48 of the 52 patients submitted to operation,