Alteration of transcription factor function is becoming a common theme in molecular mechanisms of oncogenesis. A recent example of this trend is the isolation and characterization of the chromosome 11p13 Wilms tumor suppressor gene, WT1. The WT1 protein contains a DNA binding domain consisting of four zinc fingers of the Cys2-His2 class and a proline-glutamine rich region capable of regulating transcription. Deletions of the WT1 gene or point mutations which destroy the DNA binding activity of the protein are associated with the development of the pediatric nephroblastoma Wilms tumor and Denys-Drash syndrome. This article reviews the role of WT1 in normal kidney development processes, the known biochemical functions of the protein and the status of identifying target genes regulated by this potentially oncogenic transcription factor.