The observation that a number of genetic mutations can result in neoplastic transformation has led many investigators to speculate that gene therapy may represent a useful approach to treat cancer. Conceptually, this application of gene therapy seems quite simple: to treat cancer, restore the correctly regulated expression of the needed tumor suppressor genes inside tumor cells and revert the transformed phenotype of such cells. However, such regulated expression has been difficult to achieve in practice. Here we describe recent efforts at such restoration via a novel approach to gene therapy that involves ribozyme-mediated repair of mutant RNA transcripts.