T cells bearing invariant gamma delta T cell antigen receptors localize to distinct epithelial sites in the adult mouse. These gamma delta T cells differ from the lymphoid alpha beta and gamma delta T cells in several ways. The epithelial gamma delta T cells appear to be the product of the earliest waves of TCR expressing cells in the fetal thymus. Additionally, the rearranged TCR junctions exhibit a distinct lack of diversity, possibly a result of the fetal origin and a specialized selection process. The use of a single invariant TCR and strict tissue localization suggest that these gamma delta T cells may provide a specialized function in the epithelial tissues distinct from that of the circulating alpha beta and gamma delta T cells.