To evaluate whether there is a restricted T cell receptor repertoire in rheumatoid synovium and to analyse the CDR3 region of the V beta families found to be more expressed in the synovial membrane than in the peripheral blood, in order to ascertain the presence of clonotypic expansion of T lymphocytes.The level of expression of individual V beta and V alpha families of the TCR was evaluated in paired synovial membrane and peripheral blood T cells from 8 female patients affected by rheumatoid arthritis, using the RT-PCR method. Nucleotide sequences of the CDR3 region of some V beta families were analysed in order to identify the presence of conserved sequences. Sequencing was carried out with the dideoxy chain termination method using modified T7 DNA polymerase.All of the V alpha and V beta families were amplified in both compartments of the 8 patients. Four patients did not show any preferential expression of the TCR alpha or beta chains in synovium compared with peripheral blood. The other 4 patients showed increased expression of one or more V alpha and/or V beta families in the synovium. We did not find any correlation between the duration of disease, rheumatoid factor status, HLA-DR type and the V gene families which were elevated in the synovium. Analysis of the CDR3 region showed the presence of conserved amino acid sequences in the synovium, but not in the peripheral blood.The V families found to be increased in 4 of the 8 patients studied were different, except for V beta 1 which was more highly expressed in 2 patients. The presence of conserved amino acid sequences in the CDR3 region is consistent with an antigen-driven T cell expansion at the site of autoimmune inflammation. These findings do not support our original hypothesis of the possible usefulness of therapy based on the inactivation or elimination of presumed pathogenic T cells using TCR-derived peptides or monoclonal antibodies against particular TCRs.