The G protein gamma subunits are members of a multigene family and are implicated in determining the specificity of receptor-G protein interaction. The gene structures for many of the gamma subunits remain to be determined. Here, we report the gene structure for the brain-specific gamma 4 subunit and its map position on a mouse chromosome. The gene (Gng4) comprises at least three exons spanning over 20 kb. The 225-bp coding region, which spans two exons, is interrupted by a large 18.2-kb intron whose position is conserved in other gamma subunit genes. There is a putative additional intron in the 5' untranslated region just upstream of the translation initiation codon. Introns are present in most of the other gamma subunits at this position. The mouse Gng4 gene is mapped to chromosome 13.