The expression of T-cell antigen receptor (TCR) Vbeta genes in autoimmune thyroid diseases (AITDs) was investigated. RNA was extracted from the thyroid tissue of 23 patients with early-stage Graves' disease, 19 patients with late-stage Graves' disease and 20 patients with Hashimoto's disease. Peripheral blood lymphocytes from patients and 20 normal subjects (controls) were analysed in parallel. AITD was found to be associated with diminished TCR Vbeta gene family utilization. In addition, AITDs appeared to select for specific TCR Vbeta families. The Vbeta3, Vbeta5 and Vbeta8 families were expressed more frequently in thyroid-infiltrating T-lymphocytes of early-stage Graves' disease than other Vbeta gene families. Selective expression was not observed in infiltrating T-lymphocytes obtained from thyroid tissue of patients with late-stage Graves' disease or Hashimoto's disease. Preferentially expressed TCR Vbeta gene families may be useful as molecular targets for targeted immunotherapy of AITDs.