The use of oral corticosteroids is associated with an increased risk of fracture, but there is limited information on the relationship between corticosteroid dose, bone mineral density (BMD), and fracture. We examined this relationship in a community population (more than 50 years) taking oral corticosteroids for chronic lung disease. Details of corticosteroid use and lifestyle were obtained by questionnaire, general practice records, and patient interview. BMD was assessed at the lumbar spine and femur and vertebral fracture by morphometric X-ray absorptiometry. Of the 117 patients who participated (median age, 69), 48% were female. Fifty-eight percent had osteoporosis (a T score of less than -2.5), and 61% had a vertebral fracture. The presence of vertebral fracture was related to BMD at the femoral neck, with an odds ratio of 1.6 for a 1 SD reduction in BMD. The cumulative prednisolone dose ranged from 3.4 to 175 g and was strongly associated with vertebral fracture, with the odds ratio between the highest and lowest dose quartiles being 4.4 (95% confidence interval, 1.04, 18.8). The difference in femoral neck BMD between the same dose quartiles was only modest, however (0.5 SD; 95% confidence interval, 0.09, 0.94). In patients taking long-term oral corticosteroids for chronic lung disease, the relationship between vertebral fracture risk and BMD is similar to that seen in other populations. Cumulative prednisolone dose is strongly related to fracture risk, and this effect is independent of its more modest impact on BMD.