T cells bearing specific yo TCR are the major lymphoid population in certain epithelial tissues. There are striking differences between these and peripheral T cells. The epithelial ye} T cells exhibit highly restricted V gene use, preferential pairing of TCR chains, and lack of diversity at the junctions creating populations of cells with virtually identical TCR in particular epithelia. Generation of certain epithelial ye} populations appears to be restricted to a discrete stage early in development. The restricted localization and expression of invariant antigen receptors may equip the epithelial ye} T cells to perform specialized functions which differ from those of circulating a {J and yb TCR+ cells. This review provides a summary of the characterization of yO T cells found in epithelial tissues and speculates on the in vivo role of these cells.