A 77-year-old man with relapsed non-Hodgkin's lymphoma, diffuse large B-cell type, was treated with naproxen, a nonsteroidal anti-inflammatory drug (NSAID), for paraneoplastic fever. A dramatic disappearance of not only the fever but also generalized lymphadenopathy was observed. Naproxen was continued, and he maintained remission for 10 months. When relapse of lymphoma occurred in spite of continuous naproxen administration, indomethacin, another type of NSAID, was tried. Surprisingly, rapid regression of lymphoma occurred again and was maintained for almost 1 year. These results indicate that NSAIDs are effective in some patients with non-Hodgkin's lymphoma.