Mutations or changes in protooncogenes and tumor suppressor genes are casually linked to human cancer pathogenesis. The RIZ gene is isolated based on the capacity its gene products to bind to the retinoblastoma tumor suppressor protein. Consistent with a potential role in the Rb pathway, RIZ may play an important role in human cancer pathogenesis. RIZ maps to human chromosome band 1p36, a region commonly altered in many types of human cancers. RIZ is the founding member of the PR-domain family of zinc finger genes. Similar to other members of this family, RIZ is involved in human cancers in an unusual yin-yang fashion. Two products are produced from the RIZ locus which differ by the presence or absence of the PR domain; the PR-plus product RIZ1 is commonly lost or underexpressed whereas the PR-minus product RIZ2 is always present in cancer cells. This yin-yang imbalance in the amount of the two RIZ products may be an important cause of malignancy.