An atypical form of valvular pulmonic stenosis is described. In this dysplasia there are characteristic clinical and angiographic findings which allow differentiation from typical pulmonic stenosis. Pathologically the dysplastic valve is tricuspid, unfused, markedly thickened and inflexible, and literally stuffs up a hypoplastic pulmonary annulus. The angiographic signs of valve dysplasia are: irregular doming; excessive thickness; hypoplastic annulus; narrowed sinuses; and very little change between diastolic and systolic configuration. Post-stenotic dilatation is uncommon. If the condition is unrecognized by the angiographer and the surgeon, and if standard valvulotomy is carried out, the results will be unsatisfactory.