Gammadelta T cells consist of multiple lineages of cells with distinct antigen receptor repertoires, tissue localization and function. Recent evidence suggests that the ordered appearance of these sublineages during development is a result of programed rearrangement of V(gamma)-gene segments. It appears that the T-cell receptor repertoire, at least of the gamma(delta) T cells with invariant receptors, is the result of site-directed rearrangement and cellular selection does not play a major role.