We have isolated the 5' flanking DNA sequences of the human gene encoding the 67,000-M(r) form of glutamate decarboxylase (GAD67), the gamma-aminobutyric acid synthetic enzyme. Transcription begins at a single promoter (P1) in adult brain but at two tandem promoters, P1 and P2, in fetal brain. P1, which is 3' to P2, resembles the promoter regions of many constitutively expressed genes, whereas P2 resembles a tissue-specific promoter. P1 contains a 10-base sequence (dec-1) that closely matches the element I cis-regulatory sequence identified in the promoter region of Drosophila 3,4-dihydroxyphenylalanine decarboxylase. Gel shift and transient expression assays demonstrate that the dec-1 sequence plays a role in the transcription of the human GAD67 gene.