The structures of the genomic DNA of the murine β1- and β4-subunits of the voltage-dependent calcium channel were mapped by comparing genomic and cDNA sequences. The gene structure analysis revealed that the murine β1 gene consists of 15 translated exons spread over 19 kb of the genome, whereas the β4 gene consists of 13 translated exons spread over 124 kb of the genome. Alternative spliced transcripts of the β1 gene were also characterized. Although the total lengths differ, these subunits have exon-intron organization similar to the murine β2- and β3-, and human β4-subunits, showing the highly conserved gene structure of this family. Furthermore, mRNA of these β-subunits is strongly expressed in dorsal root ganglion neurons, which have many voltage-dependent calcium channels.