The mouse Tyrp1 deletion complex is a valuable resource for high-resolution mapping of genes and phenotypes to the central region of Chromosome (Chr) 4. The distal part of the complex is homologous to human Chr 9p21-23, and we have used the available radiation hybrid maps to identify human transcripts in the region. We localize seven genes to a human YAC contig that spans the full extent of the distal deletion complex and show that the mouse homologs of four of these, including Cer1, map within the complex. On the basis of location and/or expression, we exclude genes as candidates for several known phenotypes in the region and identify a candidate transcript for the neonatal lethal phenotype l(4)Rn2.