This report documents the presence of clonal gamma delta T-cell receptor (TcR) population in the blood of a patient who presented with an arthropathy of undetermined cause, leucopenia and splenomegaly. There was no evidence for lymphoid malignancy clinically or at post-mortem. The phenotype and genotype of the clonal T-cell population were not associated with the predominant TcR delta rearrangement found in peripheral blood gamma delta cells, but were similar to those found in gamma delta TcR cells infiltrating rheumatoid synovium. The data indicate the presence of a monoclonal population of gamma delta cells TcR cells which in the face of continued immunosuppression behaved benignly. The case may represent a cytomorphologically atypical example of the large granular lymphocytes, neutropenia and arthropathy syndrome/lymphoproliferative disease of granular lymphocytes and, although the patient's clinical features were not 'classical', rheumatoid arthritis (RA) may have been the underlying primary disorder.