OBJECTIVE The epidemiological and clinical characteristics, treatment and evolution of osteoarthritis by Haemophilus influenzae type b (HIB) are reviewed since there has been little published on this subject in our country. METHODS The clinical histories of the 7 children with osteoarthritis due to Hib infection are reviewed. The diagnostic criteria included classical signs and symptoms of septic arthritis, radiological alterations compatible with joint infection and isolation of microorganisms in joint effusion and/or in the blood. RESULTS During a 24-year period (1973-1996), 248 cases of invasive infection by Hib were documented. Seven cases (2.82%) had osteoarticular infections. The ages were between 5 and 7 years and there were more males than females (71.4% vs. 28.6%). Four children/58%) had previous upper respiratory infections (URI). The microorganism was isolated in the joint effusion in 5 children and in the blood sample of the other 2. C-reactive protein was high and radiology showed alterations in 100% of the cases. Surgical treatment with articular drainage was necessary in 5 children/71.4%). In 6 cases (85.7%) initial medical treatment was i.v. beta-lactam antibiotics for 2-3 weeks followed by oral antibiotic treatment for a minimum of 6 weeks. Three children (42.8%) had sequelae. CONCLUSIONS Early diagnosis of bacterial osteoarthritis by Hib is difficult. Final therapeutical success depends on an early clinical diagnosis and aggressive multidisciplinary treatment. Drainage of the hip joint is mandatory for successful outcome. Currently, arthritis by Hib can be avoided and its sequelae prevented by vaccination.