Surgical treatment of pulmonary stenosis may lead to inevitable valvular incompetence. The hemodynamic and clinical significance of post-operative pulmonary insufficiency (PI) is uncertain. In patients presenting cardiomegaly and reduced exercise tolerance reoperation may be considered. However, pulmonary valve replacement remains controversial. In order to elucidate the relevance of PI in the long-term post-operative course, quantitative data of PI were compared with chest radiographs and the physical condition. Thirty-one patients with a mean age of 18.5 years (3-36 years) were studied. Twenty-two patients had surgical correction of Tetralogy of Fallot (TOF) and nine had commissurotomy of pulmonary valve stenosis (PS). Catheterization was performed, on average, 12.9 years (2-29 years) after operation in 68% of cases with an interval of more than 10 years. PI was quantitated by digital roentgen densitometry. Regurgitant fraction (RGF) ranged between 13-61%, according to a right ventricle volume load index (VBI) of 1.15-2.6 (ratio of total to effective stroke volume). Twenty of 31 patients (12 TOF, 8 PS) had PI as the only significant lesion. VBI (1.15-2.6) correlated with the cardio thoracic ratio (0.50-0.64), r = 0.74. All patients were in good physical condition. 11 actively took part in sports: all of the eight patients studied by ergometry met normal conditions. Four patients had antiarrhythmic medication. Eleven of 31 patients had PI and additional abnormalities: tricuspid insufficiency (4), right ventricular pressure overload (5), ventricular septal defect (1), depressed left ventricular function (5), and aortic insufficiency (3).(ABSTRACT TRUNCATED AT 250 WORDS)