Infections due to pneumococci are frequent in patients infected with the human immunodeficiency virus (HIV), but joint infections are rare. We observed two cases of septic arthritis due to pneumococci in two non-haemophilic HIV seropositive patients. In the first case, a 31-year old drug addict who had undergone splenectomy, developed hip joint infection during an episode of meningitis due to pneumococci. The germ was moderately sensitive to ampicillin. The second case involved the knee joint in a 29-year-old woman who developed pneumococcal pneumonia after a trip to Zaire. In both cases, joint infection developed after antibiotics had been initiated, and in the first case, after the infection appear to be under control. This would be similar to "post-infectious" arthritis described in gonococcal and meningococcal infections. In HIV positive patients, joint infections are rare compared with other types of immunodepression, but can be observed in all stages of the disease. A total of 75 cases have been reported in the literature, including 8 cases due to pneumococci. These joint infections could be another argument in favour of anti-pneumococcal vaccination in HIV positive patients.