In some patients with rheumatoid synovitis the distribution of V delta gene families used by freshly isolated T lymphocytes from the synovial fluid and peripheral blood is different: peripheral blood T lymphocytes preferentially use the V delta 2 gene segment, whereas the majority of synovial fluid T lymphocytes use the V delta 1. The antigenic diversity of T cell receptor gamma/delta is mainly dependent upon base sequences in the V-J junction. In the present study we investigated whether the synovial fluid T lymphocytes expressing the V delta 1 gene segment were derived from a polyclonal or monoclonal expansion. The sequences encoding the V-J junctions of 11 cDNA clones derived from the synovium of two patients with chronic arthritis were determined. Our data demonstrate that the V delta 1 cDNA clones have different V-J junction sequences. This indicates that the V delta 1-expressing T cells found in the synovial compartment are polyclonally expanded.