Eleven cases of infectious arthritis occurring in patients with rheumatoid arthritis are reported. Staphylococcus aureus was the causative organism in eight patients. Streptococcus anginosus and Streptococcus agalactiae in one patient each, and Mycobacterium tuberculosis in two patients. The mean duration of symptoms before diagnosis was 16 days in patients with pyogenic arthritis. The diagnosis of joint infection caused by Mycobacterium tuberculosis was especially delayed (57 days). Four patients died; they were found to have a longer time to diagnosis and two of them had multiple joint infection. Although Staphylococcus aureus is the microorganism most often affecting patients with rheumatoid arthritis, infection caused by Mycobacterium tuberculosis must also be considered in such patients.