The vertebrate Unc5 genes, like their Caenorhabditis elegans counterpart, define a family of putative netrin receptors. One member of this family, Unc5h3, has been shown to have an important role during cell migration in the developing murine cerebellum. Mice homozygous for mutations in Unc5h3 are ataxic and have cerebellar hypoplasia and laminar structure defects. In addition, these mice have ectopic granule and Purkinje cells in the midbrain and brainstem. We have identified the human homologue of this gene, UNC5C, and shown it to have a restricted expression pattern in adult human tissues. By radiation hybrid analysis, we have determined that UNC5C localizes to chromosome 4q21-q23 between markers D4S1557 and D4S836 and is closely linked to the Parkinson disease gene.