Contemporary reports on surgery for horseshoe kidney (HK) still recommend isthmotomy and lateropexy to complete an open pyeloplasty. To evaluate whether simple Anderson-Hynes pyeloplasty without symphysiotomy is effective for relief of ureteropelvic junction obstruction (UPJO) in HK, we studied the records of ten children, two of whom had bilateral UPJO. Only one child presented with calculi; 11 units were operated upon for UPJO, 1 needed a partial nephrectomy. The surgical outcome was evaluated with emphasis on the changes in renal drainage and function assessed by ultrasonography and diuretic renal scans. Associated vesicoureteral reflux was observed more often (25%) than with UPJO in normal kidneys. Obstruction was caused by a crossing lower-pole vessel in three cases, a high ureteral insertion in two and narrowing of the UPJ 7. Postoperative follow-up (mean 5.5 years) revealed improved renal function and good drainage in all cases. Hydronephrosis vanished in 7, whereas grade 2 hydronephrosis remained in two children with former refluxive megaureter and grade 3 in one. All children are doing well and have no symptoms due to the persistent isthmus (Rovsing syndrome). It is concluded that simple Anderson-Hynes pyeloplasty via a flank incision is a highly effective and safe procedure for treating UPJO in HK.