We have cloned the gene encoding the murine D3 dopamine receptor and have analyzed its intron-exon structural organization, to gain a better understanding of the detailed architecture of the D2 dopamine receptor genes. Restriction and sequence analysis reveal the presence of six introns, in contrast to the five introns previously reported for the rat D3 receptor. The extra intron is located in the receptor's putative third cytoplasmic loop and generates an intron-exon organization directly analogous to that found in the D2 receptor gene. In addition, we have sequenced the 5' and 3' nontranslated sequences flanking the coding region and have identified a putative poly(A) adenylation signal. These sequences are found to have a far lower homology with the corresponding rat nontranslated sequences than is found for the D2 receptor, suggesting that the control of D3 receptor expression may vary more between species than the control of D2 receptor expression.