Molecular cloning of cDNAs encoding distinct G-protein β- and γ- subunit types has shown that these subunits comprise families of proteins in mammalian tissues, cDNAs encoding four different β subunits and seven different γ subunits have now been identified. All the cDNAs were isolated using appropriate oligonucleotide probes. Two broadly different approaches have been used to isolate the cDNAs. The first method involves screening a cDNA library with oligonucleotide mixtures specific to the amino acid sequence of a protein. The second method is based on the polymerase chain reaction (PCR). In this method oligonucleotide mixtures specific to the amino acid sequence of a protein or specific to conserved amino acid residues among members of a family of proteins are used as PCR primers for amplifying a portion of the cDNA. Analysis with specific antibodies has revealed that purified G-protein βγ protein complexes from different sources are mixtures of β and γ subtypes. In addition, subtypes exist that are distinct from those for which cDNAs have been identified.