The murine chromosomal gene for the GABAA receptor delta subunit was isolated and characterized by high-resolution mapping and DNA sequencing. Spanning 13 kb, it comprises nine exons and displays an intron pattern comparable, but not identical, to that seen in members of the nicotinic acetylcholine receptor family. Notably, the second transmembrane domain thought to line the ion channel and conserved among different GABAA receptor subunits, is interrupted by an intron. The 5'-flanking region of the delta gene displays features characteristic of a CpG island and lacks canonical promoter elements such as TATA and CCAAT consensus sequences in proximity to the transcriptional initiation site. The human delta subunit gene was localized on the short arm of chromosome 1.