Between January 1985 and August 1995, among 242 patients who underwent a modified Fontan procedure, 99 had atrioventricular valve regurgitation ranging in degree from 1 to 4, for which concomitant repair of the atrioventricular valve regurgitation was done in the majority of cases. In all but 4 cases the atrioventricular valve was repaired mainly by circular annuloplasty and valve replacement was not done in any case. Although the hospital mortality rate was significantly higher in cases with atrioventricular valve regurgitation (12/99, 12%) than in cases without (4/143, 3%; p < 0.0037, chi 2 test), actuarial survival in atrioventricular valve regurgitation was 84% for years 5 through 10. The degree of atrioventricular valve regurgitation before operation was 1.6 +/- 0.7 on average: in 49 cases with higher than grade 2 regurgitation before operation there was a significant decrease to 0.4 +/- 0.49 (p < 0.0001) after operation in short-term survivors. Patients with atrioventricular valve regurgitation can be treated with reasonable risk, provided proper repair of the valve is done. Circular annuloplasty is a simple and uniformly effective method to control regurgitation even in cases of common atrioventricular valve.