We have used the polymerase chain reaction technique (PCR) to clone the cDNA of the D2 dopamine receptor from rat striatal mRNA. Two major PCR products were produced; one product was identical to a previously published rat cDNA, while the other, more abundant product differed only by an 87-nucleotide insert located in the region of the putative third cytoplasmic loop of the D2 receptor. A PCR approach for determining message abundance was used to determine the relative message abundance of the two forms of the D2 receptor in a variety of tissues. Possible implications of the two forms of the D2 receptor for dopamine-mediated signal transduction are discussed.