Abstract: Inactivation of Wilms´ tumor X (WTX) gene has been linked to the pathogenesis of a varying percentage of nephroblastomas. In contrast, germline mutations of WTX were identified to cause bone dysplasia, but not to induce the development of nephroblastomas. In our study we investigated whether tumor promotion of nephroblastoma by inactivation of WTX gene is linked to certain single nucleotide polymorphisms (SNPs). Therefore 8 SNPs—distributed over the whole length of the WTX gene—were investigated by high resolution melting curve analysis (HRMA) and sequencing of genomic DNA from nephroblastoma patients (NB) and controls. No difference was detected in the 8 SNPs investigated, which were distributed over the whole length of the gene. Additionally, sequence analysis of the coding part of the WTX gene of the tumor samples revealed no chromosomal aberration. Our study indicates, that inactivation of WTX appears to be a late event in tumorigenesis of nephroblastoma in a subgroup of nephroblastomas.