Felty syndrome, comprised of neutropenia, rheumatoid arthritis and splenomegaly, occurs in approximately 1% of patients with rheumatoid arthritis. Up to one third of these patients have an increased number of large granular lymphocytes. The usual immunophenotype of these cells is CD3+, CD8+, CD57+, T cell receptor (TCR) alpha beta. A patient with Felty syndrome and large granular lymphocytosis, who had an unusual immunophenotype CD3+, CD4-, CD8-, TCR gamma delta, is described. Her neutropenia responded to treatment with granulocyte colony stimulating factor (G-CSF), which was given in order to raise her neutrophil count prior to bilateral knee replacement surgery. Thus, Felty syndrome with large granular lymphocytosis is a heterogeneous condition, one in which TCR gamma delta large granular lymphocytosis may be found, and also shows a response to treatment with G-CSF.