W e have investigated the T cell receptor V alpha and V beta gene family usage by T lymphocytes infiltrating affected thyroids in patients with autoimmune thyroid disease. We show that the intrathyroidal T lymphocytes from patients (n = 6) with autoimmune thyroid disease display a widespread usage of V beta gene families with an average of 14.4/19 V beta gene families similar to the peripheral T lymphocytes of the same patients. Because we recently reported that the utilization of V alpha gene families is markedly reduced within these mitogen-stimulated intrathyroidal T cell populations, as well as within intact tissue from similar patients (n = 4) (overall mean of 4.0/18 families detected), these results indicate that in thyroids of patients with autoimmune thyroid disease the lymphocytes are selectively accumulating based on their V alpha rather than V beta elements. This preferential hTcR V alpha and widespread V beta gene usage was not mimicked in most 7-d autologous mixed lymphocyte reactions using non-T cell stimulators (n = 6) or EB-virus immortalized autologous B cell lines (n = 3). Hence, the selective V gene utilization by intrathyroidal T cells is likely to be secondary to multiepitopic thyroidal autoantigens activating thyroid infiltrating T cells or to the presence of a superantigenlike thyroidal self-antigen, capable of determining a selective infiltration or activation of a variety of T lymphocytes on the basis of their V alpha gene usage.