Surgical repair of tetralogy of Fallot (TOF) frequently results in pulmonary valve insufficiency. Nevertheless, no serial information is available on the long-term impact of the valvular insufficiency on right and left ventricular function. Right and left ventricular ejection fraction was measured serially by radionuclide angiocardiography in 21 patients with at least moderate pulmonary insufficiency after repair of TOF. A baseline study was obtained an average of 1.2 years after repair, and a follow-up study was performed an average of 10.2 years after surgery. Changes in ventricular function over time and deviations from the normal range were analyzed. At baseline evaluation the mean right ventricular ejection fraction (RVEF; 0.52 +/- 0.10) and left ventricular ejection fraction (LVEF; 0.68 +/- 0.10) were normal. At the time of follow-up the mean RVEF had significantly decreased to 0.45 +/- 0.09 (p < 0.01). The mean LVEF had decreased to 0.60 +/- 0.11 (p < 0.02). This change was independent of the RVEF (r = -0.13). Eleven patients (52%) had an abnormal RVEF or LVEF at follow-up. Nineteen patients (90%) showed a decrease of 0.05 or more in RVEF, LVEF, or both between studies. These data suggest a negative impact of long-standing pulmonary insufficiency on right and left ventricular systolic function after repair of TOF. Therefore, continued surveillance of biventricular function in this patient population appears warranted.