We have isolated a mouse cDNA which codes for a functional type 1 sigma receptor. The functional identity of the cDNA was established by expressing the cDNA in mammalian cells and measuring the cDNA-induced binding of haloperidol. Using this cDNA as the probe, we have isolated a murine genomic clone which contains the type 1 sigma receptor gene in its entirety. We have sequenced the gene completely, deduced the exon-intron organization and analyzed the promoter region sequence for transcription factor binding sites. The gene (approximately 7 kbp) is TATA-less but contains CCAATC and GC boxes immediately upstream of the transcription start site. The gene consists of 4 exons and 3 introns. The 5'-flanking region contains putative binding sites for AP-1, AP-2, GATA-1 and steroid receptors.