α1-Adrenergic receptors (α1-ARs) play critical roles in the regulation of a variety of physiological processes. Increasing evidence suggests that multiple receptor subtypes of α1-ARs regulate these physiological processes. Molecular cloning has identified three distinct cDNAs encoding α1-AR subtypes (α1A, α1B and α1D) that are structurally homologous. Among the α1-AR subtypes, the function of the α1D-AR remains unclear. In order to examine the physiological role of a1D-AR, we cloned and characterized a gene for the mouse α1D-AR. Using a mouse α1D-AR cDNA as a probe, we isolated the gene for the mouse α1D-AR from a mouse genomic library. The α1D-AR consists of two exons and an intron that interrupts the coding region of the putative sixth transmembrane domain. The 5′-flanking region of exon 1 contains neither a TATA box nor a CAAT box but is high in GC content and contains several Sp1 binding sites (GC boxes). This pattern is similar to promoters described for other members of α1-ARs. The untranslated region also contains putative cyclic AMP response elements. Isolation of this gene will allow further investigation, via gene knock-outs and deletion mutants, of the mechanisms of transcriptional regulation and a greater understanding of the physiological role of α1D-AR.