We conducted clinicopathologic and immunohistochemical analyses of the prevalence of Epstein-Barr virus (EBV) among 24 patients with malignant lymphoma complicating systemic rheumatic diseases. (SRD) These 24 patients included 17 with rheumatoid arthritis (RA), 3 with systemic lupus erythematosus (SLE), 2 with systemic sclerosis (SS), and 2 with dermatomyositis (DM). There were 2 men and 22 women ranging in age from 30 to 86 years (mean: 64 years). The interval between the onset of rheumatic disease and that of malignant lymphomas ranged from 3 months to 35 years (mean: 142 months). The use of immunosuppressive drugs before the onset of malignant lymphoma was recorded in 15 patients. Among them, 5 patients received methotrexate (MTX) therapy. Malignant lymphomas were found at extranodal sites in 9 patients, and the disease was in the advanced stage in 17 patients. Histologic and immunohistochemical studies demonstrated that 18 cases (75%) were B-cell lymphoma (RA=12, SLE=2, SS=2, DM=2), 3 (12.5%) were peripheral T-cell lymphoma (RA=3), and 3 (12.5%) were classical Hodgkin lymphoma (RA=2, SLE=1). As in previous reports, there was an increased frequency of diffuse large B-cell lymphoma (50%) in the present series. Moreover, a majority of the diffuse large B-cell lymphomas exhibited activated B-cell phenotype. EBV-encoded small RNAs (Epstein-Barr early region [EBER]-) and/or LMP-1+tumor cells were identified in only 3 cases of classical Hodgkin lymphomas. Our findings suggested EBV-associated lymphoma comprised only a small fraction of all non-Hodgkin's lymphomas in the general SRD patient population.