Felty's syndrome (FS), which comprises rheumatoid arthritis (RA), neutropenia, and often spleno-megaly, occurs in 1% of RA patients. Although neutropenia is the most prominent feature, other hematologic abnormalities including anemia, lymphopenia and thrombocytopenia, have been described to various extension. Infection is the major cause of death in FS. Most of infections are caused by bacteria. Opportunistic infections are rare, because the incidence of infection is, in general, related to the degree of neutropenia. Peumocystis carinii pneumonia (PCP) is an opportunistic infection in immune compromised patients with acquired immune deficiency syndrome (AIDS), hematologic malignant disorders, organ transplantation, solid tumor and inflammatory rheumatic disease. We experienced PCP in a patient with FS who had neutropenia and lymphopenia.