Alveolar soft part sarcoma and pediatric renal cell carcinoma share a similar chromosomal abnormality, t(X;17)(p11.2;q25). Recently, it has been suggested that the inactivation of DNA mismatch repair genes hMLH1 and hMSH2 may play an additional role in the pathogenesis of alveolar soft part sarcoma. Immunohistochemical expression of the proteins hMLH1 and hMSH2 is indicative of the activation status of the corresponding genes. We performed immunohistochemistry for hMLH1 and hMSH2 in 4 cases of pediatric renal cell carcinomas with Xp11.2 rearrangements. All cases showed nuclear immunoreactivity for both proteins, although the staining was patchy. Our study demonstrates that inactivation of the DNA mismatch repair genes hMLH1 and hMSH2 does not appear to play a role in the tumorigenesis of pediatric renal cell carcinomas with Xp11.2 rearrangements.