In 30 patients in whom osteomyelitis was suspected fine-needle bone biopsies (FNBB) were taken at the same time as bone was aspirated for bacteriological examination. The diagnosis of osteomyelitis was eventually confirmed in 15 patients; the other 15 had myositis (3), arthritis (3), trauma (2), microgeodic phalangeal syndrome (2), haematoma in a non-ossifying fibroma (1), and Ewing's sarcoma (1). In three patients no pathology was found. The temperature, WBC and ESR at presentation did not help to distinguish osteomyelitis from other conditions. FNBB, however, proved to be a useful additional investigation with a sensitivity for osteomyelitis of 87% and a specificity of 93%.