A 69-year-old woman, who had suffered from deforming rheumatoid arthritis since the age of 40 years, had been treated with methotrexate for 3 years. She presented with a 7 week history of neck lymphadenopathy. Biopsy revealed low-grade marginal-zone B-cell non-Hodgkin's lymphoma. Computerized tomography and bone marrow biopsy confirmed stage IIIA disease. Spontaneous complete remission of the lymphoma was achieved 14 months after withdrawing immune suppression with methotrexate.