Dr. Risch, a statistical geneticist, genetic epidemiologist, and population geneticist is involved in a variety of projects of both a theoretical and applied nature. These studies include both clinical and population genetic projects. He has developed novel tools and approaches for the mapping and identification of genetic variants underlying both Mendelian and non-Mendelian diseases. For example, he contributed to the cloning of genes for torsion dystonia and hemochromatosis. He defined admixture mapping in ethnically admixed populations as a tool for gene discovery and has applied it to such diseases as hypertension and lipidemia.