Background and aims: The outcomes of nephroblastoma (Wilms’ tumor, WT) in our institute and otherdeveloping countries are notably below results in most developed countries. The objective of this study was toreview treatment outcomes of pediatric nephroblastoma in southern Thailand during the past decade and attemptto isolate factors associated with a poor prognosis. Patients and methods: The records of 34 WT patients, agedless than 16 years, who were operated on in Songklanagarind Hospital, Thailand, during the period from January1996 to December 2007 were reviewed. The management protocol followed the scheme of the US NationalWilms Tumor Study Group (NSWTG). Results: Thirteen cases (38.2%) were diagnosed as stage I, 4 (11.8%) asstage II, 13 (38.2%) as stage III and 2 (5.9%) as stage IV. Two cases with bilateral disease (stage V) had stage Itumors in both kidneys. Four-year overall survival (OS) and event free survival (EFS) rates were 65.2% and52.7%, respectively. Univariate analysis by Log-rank test revealed statistically significant associations betweenOS and nodal status (p- value < 0.01), manifestation of gross hematuria (p-value 0.02), and tumor size of 10centimeters or more (p-value 0.02). Multivariate analysis found only the nodal status to be independentlyassociated with OS at a Hazard Ratio of 16.6 (p-value < 0.01). Eight of 13 stage I cases and 6/13 stage III caseshad relapsed, with two-year post-relapse survival of 42.8%. Significantly poorer outcome was found in caseswith early relapse within 200 days after enrollment (p-value 0.02). Conclusion: The poor outcome of pediatricnephroblastoma in southern Thailand seems to be related at least in part to failures in primary treatment instage I patients. Large tumor size and gross hematuria were associated with risk of a poorer outcome.