The T cell antigen receptor (TCR) delta gene is located within the TCR alpha locus. A T cell-specific transcriptional enhancer, distinct from the TCR alpha enhancer, has been identified within the J delta 3-C delta intron of the human T cell receptor delta gene. This enhancer activates transcription from the V delta 1 and V delta 3 promoters as well as from heterologous promoters. Enhancer activity has been localized to a 250-bp region that contains multiple binding sites for nuclear proteins. Thus, transcriptional control of the TCR delta and TCR alpha genes is mediated by distinct regulatory elements.