Congenital pulmonic stenosis may be defined as consisting of structural changes in the subpulmonary tract, the pulmonic valve, or the pulmonary trunk that result in a gradient between the systolic pressure in the right ventricle and that in the pulmonary artery. From a developmental point of view, the valvular type of pulmonic stenosis may be the outcome of fetal endocarditis of the pulmonary cusps1 or, as Gross has suggested, the result of maldevelopment of the arteries that supply the valves, with consequent infarction and fibrosis.2 There is agreement on the embryology of infundibular stenosis; the idea of Keith is usually accepted that infundibular stenosis is due to an arrest of the normal involution of the bulbus cordis, which should form a part of the right ventricle by the end of the second month.3 ANATOMIC AND PHYSIOLOGICAL FACTORS Anatomically, pulmonic stenosis usually is not an isolated malformation. As