A rat brain cDNA probe was used to localize a gene encoding the α1 subunit of neuronal dihydropyridine-sensitive L-type calcium channels in the mouse and human genomes. Hybridization of the probe to Southern blots made with DNAs from a Chinese hamster × mouse somatic cell hybrid panel indicated that this gene maps to mouse chromosome 14 (Chr 14). Southern blot analysis of an intersubspecies cross demonstrated that the calcium channel α1 subunit gene, termed Cchl1a2, can be positioned 7.5 cM proximal to Np-1. Similarly, segregation among human X rodent somatic cell hybrids indicated that CCHL1A2 maps to human chromosome 3. These assignments are consistent with a region of linkage homology between human chromosome 3p and a proximal region of mouse Chr 14.