BACKGROUND: Approximately 5% of children with Wilms tumor present with bilateral disease. The treatment challenge is to achieve a high cure rate while maintaining adequate long-term renal function. The authors of this report assessed the feasibility and outcome of nephron-sparing surgery in patients with bilateral Wilms tumor who were treated at a single institution. METHODS: A retrospective review was performed of all children who were treated at St. Jude Children's Research Hospital for synchronous, bilateral Wilms tumors from 1999 through 2006. Imaging studies, surgical techniques, and pathology reports were reviewed. The outcomes evaluated included surgical complications, tumor recurrence, renal function, and patient survival. RESULTS: Twelve patients with synchronous, bilateral Wilms tumors were identified, including 10 patients who underwent successful bilateral nephron-sparing procedures. One patient who presented with renal failure and anaplastic histology underwent bilateral nephrectomies, and 1 patient with intra-atrial tumor extension underwent an ipsilateral nephrectomy/thrombectomy and subsequent contralateral partial nephrectomy. Postoperative complications included persistent urine leak in 3 patients, macroscopic residual tumor in 2 patients, and pyelonephritis in 1 patient. Long-term complications included local tumor recurrence in 2 patients, intestinal obstruction in 2 patients, ureteropelvic junction obstruction in 1 patient, and renal failure in 1 patient. The overall survival rate was 83% (mean follow-up, 3.9 years); both patients who died had bilateral, diffuse, anaplastic histology. CONCLUSIONS: All patients who had bilateral Wilms tumors with favorable histology, except for 1 patient who had extensive tumor thrombus, underwent successful bilateral partial nephrectomies. Complications were minimal, and long-term renal function and survival were excellent. From this experience, the authors concluded that bilateral nephron-sparing surgery should be considered for all patients who have bilateral Wilms tumor with favorable histology, even if preoperative imaging studies suggest that the lesions are unresectable.