Oral corticosteroids are known to increase the risk of fracture in adults, but their effects in children remain uncertain. The medical records of general practitioners in the United Kingdom (from the General Practice Research Database) were used to estimate the incidence rates of fracture of children ages 4-17 years taking oral corticosteroids (n = 37,562) and of control children taking nonsystemic corticosteroids (n = 345,748). Each child with a fracture (n = 22,846) was subsequently matched by age, sex, practice, and calendar time to one child without a fracture. The average duration of treatment was 6.4 days (median, 5 days). The risk of fracture was increased in children with a history of frequent use of oral corticosteroids; children who received four or more courses of oral corticosteroids had an adjusted odds ratio (OR) for fracture of 1.32 (95% CI, 1.03-1.69). Of the various fracture types, the risk of humerus fracture was doubled in children who received four or more courses of oral corticosteroids (adjusted OR, 2.17 [1.01-4.67]). Fracture risk was also increased among children using 30 mg prednisolone or more each day (adjusted OR for fracture, 1.24 [1.00-1.52]) and among those receiving four or more courses of oral corticosteroids (OR, 1.32 [1.03-1.69]). Children who stopped taking oral corticosteroids had a comparable risk of fracture to those in the control group. Our findings suggest that children who require more than four courses of oral corticosteroid as treatment for underlying disease are at increased risk of fracture. It is not entirely clear whether this relates directly to oral corticosteroid use or the underlying disease and its severity. Irrespective of these issues, this group of children is at increased risk of fracture.