We reviewed 275 cases and calculated the prevalence of bacteriologically or radiologically confirmed acute haematogenous osteomyelitis in children under 13 resident in Greater Glasgow during 1970 to 1990. In the 20-year period there was a fall of over 50%, mainly involving cases of long-bone infection, and those due to Staphylococcus aureus. There was a reduced incidence of complications. The proportion of cases involving long bones decreased from 84% to 57%, and those of Staphylococcus aureus infection from 55% to 31%. These changes, in what is becoming a rare disease, need to be known to ensure early diagnosis and adequate treatment, particularly of subacute non-staphylococcal infection at unusual sites.