Felty's syndrome is characterized by neutropenia, splenomegaly, and leg ulcers in patients with rheumatoid arthritis. The pathogenesis of the neutropenia is an immune-mediated process that involves immune complexes, antineutrophil antibodies, and abnormal white cell kinetics. We prescribed salazosulfapyridine to a 65-year-old woman with this syndrome. The neutropenia improved along with a reduction in neutrophil-bound IgG, demonstrated by flow cytometric analysis. Salazosulfapyridine may be of benefit for the treatment of Felty's syndrome, and flow cytometry can be used to monitor disease activity and therapeutic efficacy.