Multiple molecules exist on the cell surface of lymphocytes that are important for development, activation and regulation of the immune response. Of prime importance in this regard is the clonotypic alpha beta heteodimer T cell receptor (TCR) that is noncovalently associated with the multicomponent CD3 complex, it has been shown that large amounts of non-disulfide linked alpha- and beta-chains are synthesized most of which are degraded before assembly into a native TCR-CD3 complex. Final processing of the TCR-CD3 complex takes place only after complete assembly of the incompletely processed TCR and CD3 chains. A model for TCR-CD3 assembly and final processing was proposed. Analyses of the gamma delta TCR revealed significant clonal diversity in expression indicating that the gamma delta TCR has the potential to recognize a variety of ligands. Furthermore, the activation properties of cells bearing gamma delta TCRs was found to be very similar to those bearing alpha beta TCRs in terms of CD3 components and responsiveness to various activation signals such as anti-Thy-1, anti-CD3, PMA and ConA. The majority of gamma delta expressing cells present in the periphery were found to be thymic dependent with a small percentage being thymic independent. Multiple forms of gamma delta TCRs were found to be present in the periphery including those containing several types of C gamma 4 chains. In addition, whereas CD3+, CD4-, CD8-, alpha beta TCR+ cells have been found in the thymus, none could be detected in the periphery.