Abstract
Functional adaptations in the right ventricular outflow tract have been discussed in relation to the development of acquired "pulmonary stenosis". It is concluded that physical forces as well as structural abnormalities may greatly influence both the clinical picture and the life history of many patients with congenital heart lesions. The importance of further serial hemodynamic studies to provide a fuller understanding of the natural course of many lesions is stressed, so that better advice about prognosis and the optimal time for surgical treatment may be given.