The effects of congenital right ventricular pressure and volume overload were studied in 3 patients with pulmonary stenosis, 7 with atrial septal defect and 6 with atrial septal defect plus pulmonary stenosis late after successful surgical correction. Gated equilibrium blood pool radionuclide ventriculography was used to measure right ventricular function at rest and during exercise and to compare it with eight normal subjects. Right ventricular ejection fractions at rest and during exercise were measured to be 61 +/- 9% and 66 +/- 13%, respectively, in the group with pulmonary stenosis, 49 +/- 7% and 54 +/- 8% in the group with atrial septal defect, and 65 +/- 13% and 69 +/- 13% in the group with atrial septal defect plus pulmonary stenosis. The values in the groups with pulmonary stenosis and atrial septal defect plus pulmonary stenosis were significantly higher than the control subjects (45 +/- 5% and 51 +/- 5%, p less than 0.01). The peak filling rate at rest and during exercise was also significantly higher in the groups with pulmonary stenosis and atrial septal defect plus pulmonary stenosis than in controls (at rest, 2.72 +/- 0.72, 2.53 +/- 0.94 vs. 1.64 +/- 0.24 p less than 0.05; during exercise, 4.38 +/- 1.23, 4.13 +/- 1.18 vs. 2.52 +/- 0.62, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)