CD3‐epsilon expression is controlled by a downstream T lymphocyte‐specific enhancer element. We report the identification of a T cell‐specific transcription factor, TCF‐1, binding to this element. The multimerized recognition motif of TCF‐1 constituted a T cell‐specific enhancer. Subsequent cloning of TCF‐1 identified three splice alternatives. TCF‐1 contained a single DNA‐binding HMG box most closely related to similar boxes in the putative mammalian sex‐determining gene SRY and in the Schizosaccharomyces pombe Mc mating type gene. TCF‐1 mRNA was expressed uniquely in T lymphocytes. Upon cotransfection into non‐T cells, TCF‐1 could transactivate through its cognate motif. These results identify TCF‐1 as a T cell‐specific transcription factor, which might play a role in the establishment of the mature T cell phenotype.