Antireflux surgery was successfully performed in 16 adults and children with bilateral or unilateral vesicoureteral reflux associated with a small pyelonephritic kidney. Although in 14 cases the preoperative 131I-Hippuran clearance of the affected unit was less than 100 ml/min/1.25 m^2, in 10 cases renal function was stabilized or slightly improved postoperatively. Only 1 child showed a severe deterioration of renal function. All 16 patients were cured of their acute pyelonephritis. Surgical correction of the reflux had no beneficial effect on renal size or renal scars. Urinary tract infection was eliminated in 12 of the 16 cases. It can be concluded that a small pyelonephritic kidney associated with a vesicoureteral reflux should not be removed even if its isotopic clearance is less than 100 ml/min.