Correlative angiographic-anatomical studies in 19 cases of pulmonary atresia with intact ventricular septum showed the following relations between angiographic appearance of the pulmonary valve and the morphology of the right ventricle. (1) Doming of the pulmonary valve was associated with a nearly normal-sized right ventricle and a wide infundibulum patent to the level of the pulmonary valve. (2) A fixed valve was associated either with (a) pronounced hypoplasia of the ventricular chamber and stenosis of the infundibulum of (b) less commonly, a massive right ventricle and Ebstein's malformation of the tricuspid valve. (3) An intermediate type valve was associated with a small right ventricle and a small infundibulum which was, however, patent to the level of the pulmonary valve. It is suggested that the configuration of the pulmonary valve is a result of haemodynamic stresses placed upon it. These stresses, in turn, are determined by the morphological nature of the right ventricle. Thus, the nature of the pulmonary valve as seen angiographically may be used as an index of right ventricular morphology.