Introduction: Wilms' tumor is the most common malignant and primary renal tumor in children. Studies, which have been done in some countries, have introduced numerous factors such as age of incidence, stage, lymphadenopathy, histopathology and etc. Effective in the survival rate of this tumor according to the importance of this tumor in children, we decided to perform a study about the survival rate of Wilms' tumor and the effective 'factors on it.Materials and methods: This is an analytic study on 128 patients affected with Wilms' tumor whom referred to the oncology ward of Hazrat-e-Ali Asghar Hospital between 1977 and 2001. In addition to the current status of the patients, demographic characteristics, signs and symptoms, laboratory studies at the time of diagnosis and the stage of the disease were recorded and ultimately survival analysis was performed using the Kaplan-Meier procedure and life table. Cox Regression was used to determine the effective factors.Results: The mean survival rate was 82.99 months. The number of patients was equal in both genders (64 patients in each gender) and the survival average did not have any significant statistical relationship with gender (power = %92.4). Most of the tumors were in stage 3 at the time of diagnosis. The survival of the patients was reducing significantly, with the progression of the stage of tumor (P = 0,002). The existence of metastasis (P=0.000, odds ratio 0.207), splenomegaly (P = 0.018, odds ratio = 0.336), and recurrent (P= 0,037, odds ratio = 0.184), were significantly reducing the survival of the patient. To determine the severity of effective factors on the survival rate of the patients Cox Regression Method was used in with, absence of metastasis and positive blood group were from well-prognosis predictive factors in these patients.Conclusion: 5-year survival rate of the patients was 63.28% in this study which was lower in comparison with the results of other studies in other countries. This can be the result of delay in consulting with medical centers, the diagnosis method and or the Referral State of this center. Recent studies have shown that age and tumor size has minimal values in the prognosis or the patients due to improvement in the quality of treatment and our study support this idea. Genetic factors will probably be used in determining the survival of these patients and also in their treatment.