The G protein γ 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 γ subunits remain to be determined. Here, we report the gene structure for the brain-specific γ4 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 γ 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 γ subunits at this position. The mouse Gng4 gene is mapped to chromosome 13.