A 74-year-old woman had been treated with methotrexate over 2 years for rheumatoid arthritis. She was admitted to the hospital because of non-healing leg ulcers. After being treated with trimethoprim-sulphamethoxazole for a urinary-tract infection, she developed severe pancytopenia, followed by pneumonia and septic shock. The patient died shortly after. Concomitant treatment with methotrexate and sulphonamides should be strongly discouraged.