Patients with systemic lupus erythematosus (SLE) are at increased risk of developing non-Hodgkin's lymphoma (NHL), but features of SLE associated with NHL are not well described. The objective of this study was to describe SLE characteristics, laboratory serologies, and medication histories in patients who subsequently develop NHL. Two thousand twenty patients with SLE were identified using the online Partners' patient database research tool between October 1992 and June 2005. We confirmed the diagnoses of SLE and NHL and sought details of medical history and treatment by medical record review. Eleven patients with NHL without coexisting rheumatoid arthritis, Sjögren's, or HIV were identified; seven of these (64%) had a diffuse large B cell lymphoma subtype, and 83% of those stained were Epstein-Barr virus (EBV) negative. The mean duration of SLE at NHL diagnosis was 17.8 years (range 1.6-41.8), and the mean Systemic Lupus International Collaborative Clinics/American College of Rheumatology damage index was 1.9. Seven patients (64%) had SLE hematologic involvement, four had anti-dsDNA antibodies, and four had anti-phospholipid antibodies. One patient had significant renal disease. All patients had arthritis and had received antimalarial therapy. Five of 11 patients had received other treatments for SLE, including cyclophosphamide, imuran, methotrexate, and/or sulfasalazine. Diffuse large B cell lymphoma was the most common subtype of NHL, and most were EBV negative. Although disease duration was fairly long and end organ damage moderately severe in this group of patients, renal disease and the use of immunosuppressive chemotherapeutic agents were rare and did not appear to confer an increased risk of NHL development.