Objective: The aim of the present study was to evaluate the clinical characteristics, factors affecting treatment approach, and longterm outcome of patients with Wilms tumor. Methods: We identified the demographic features, mode of presentation, applied treatments, and long-term outcomes of 88 patients treated between 1990 and 2011 at Hacettepe University İhsan Doğramacı Children's Hospital according to the Turkish Pediatric Oncology Group protocol. Data were analyzed using SPSS program, and

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... -square test was used for statistical analysis. Results: The study included 88 patients (50 females and 38 males) with a mean age at presentation of 3±2.48 years. Patients were classified as stage 1 (n=35, 39.8%), stage 2 (n=16, 18.2%), stage 3 (n=17, 19.3%), and stage 4 (n=20, 22.7%). Pathological examination of tumors revealed favorable histology in 76 (86.4%) patients and unfavorable histology in 10 (11.4%) patients. Forty-nine (55.6%) patients received preoperative chemotherapy, and patient's age at diagnosis and physical examination findings influenced the decision of the administration of preoperative chemotherapy (p<0.05). Of the 88 patients, 25% aged <1 year and 75% aged between 3 and 5 years received preoperative chemotherapy. The palpated mass was crossing the midline in 20.5% of patients who were subjected to primary surgery. Tumor ruptured in 5.6% of patients intraoperatively. Long-term prognosis of patients was as follows: 68 (83.9%) children were cured and 13 (16%) children died due to recurrences and metastases. Survival rates reached 100% in stage 1 and 2 patients but decreased to 75% and 50% in stage 3 and 4 patients, respectively. Conclusion: Age at presentation and physical examination findings are significant in surgical planning. Stage is the most important prognostic factor. Patients with Wilms tumor are treated with low complication and high survival rates due to multidisciplinary treatment approach at our institution.