The bacterial artificial chromosome (BAC) clone 56I19 containing the mouse GAD67 gene (and 60 kb of upstream and downstream sequence) was modified by insertion of an Enhanced Green Fluorescent Protein (EGFP) cDNA and phosphoglycerate kinase polyadenylation sequence in the first coding exon at the translation initiation site of the GAD67 gene. This GAD67-GFP BAC was microinjected into fertilized C57BL/6 mouse eggs. Mice (line G42) selectively express enhanced green fluorescent protein (EGFP) in the calcium-binding protein parvalbumin (Pv)-expressing subclass of basket interneurons (soma, dendrites, and axons) and also in putative presynaptic boutons. Transgene expression (EGFP expression) is detected as early as embryonic day 14 (E14) with high expression levels throughout postnatal development.