The outcome of primary management of acute osteomyelitis in 655 children treated in New Zealand between 1947 and 1976 is examined. Failure occurred in 20 per cent of children, in four-fifths of whom it was manifest by one year, and half of whom experienced one recurrence only. Lower failure rates were associated with use of bactericidal antibiotics, certain favourable sites, and age over 16 years. Surgical intervention was associated with significantly higher failure rates. The place of surgical intervention and the optimal duration of antibiotic treatment can only be determined by prospective clinical trials.