A retrospective analysis of 332 children with osteomyelitis (OM), managed from 1966 to 1996, was undertaken to evaluate etiology, clinical course and treatment results. In 64% of all patients positive bacterial cultures were obtained, Staphylococcus aureus, streptococci, pneumococci, and Haemophilus influenzae were the most frequently cultured pathogens. In two-thirds of the cases long bones (femur, tibia, humerus) were affected. Osteoarthritis or suppurative arthritis was evident in 27%; 32 of 170 (19%) re-evaluated patients had moderate or severe sequelae. Risk factors for an unfavorable course were the onset of disease in early infancy, suppurative arthritis, and an affected epiphysis. Suppurative arthritis, in particular, needs early evacuation to prevent sequelae. In recent years we observed an increasing number of patients presenting with atypical forms of OM. Since 1989 10 patients were considered to have chronic recurrent multifocal OM (CRMO). In 6 of them the clavicle was involved; their ages ranged from 3 to 14 years. The erythrocyte sedimentation rate was elevated (median 48, range 9-110 mm), while other inflammatory parameters like C-reactive protein (median 9, range <5-85 mg/l) or leucocyte count were slightly elevated or normal. Histopathology was stage-dependent, with a predominance of lymphoplasmacellular infiltration. A nonbacterial origin of CRMO is probable but not proven. Histopathology is not suitable for differentiation between bacterial and nonbacterial forms of bone inflammation.