Complementary DNAs were isolated and used to deduce the primary structures of the α₁ and α₂ subunits of the dihydropyridine-sensitive, voltage-dependent calcium channel from rabbit skeletal muscle. The α₁ subunit, which contains putative binding sites for calcium antagonists, is a hydrophobic protein with a sequence that is consistent with multiple transmembrane domains and shows structural and sequence homology with other voltage-dependent ion channels. In contrast, the α₂ subunit is a hydrophilic protein without homology to other known protein sequences. Nucleic acid hybridization studies suggest that the α₁ and α₂ subunit mRNAs are expressed differentially in a tissue-specific manner and that there is a family of genes encoding additional calcium channel subtypes.