Corticosteroid use is one of the most important secondary causes of osteoporosis. Generally, it has been believed that in addition to its effect on bone mineral density (BMD), it also causes an alteration in bone quality that means that fractures occur at a lower BMD than might be expected. To establish if this is the case, we have compared the relationship between BMD and vertebral fracture in patients receiving corticosteroids with that in patients who had never received such therapy. Information was gathered on those patients who had been referred to the participating centers and had both BMD measurements and lateral thoracolumbar radiographs. In all, 452 patients (391 female) were identified; of these 82 (63 female) were receiving corticosteroids. There was no significant difference in BMD between the patients on corticosteroids and those with other suspected causes of osteoporosis. Vertebral fractures were present in 53% of patients on steroids compared with 35% of those who had no such treatment (p = 0.0035). The fractures were more likely to be multiple in patients on corticosteroids (p = 0.0042). However, if the relationship between bone density and fracture is investigated by plotting the cumulative prevalence of fracture against the bone density, measured by T score, the median BMD for fractures actually was marginally lower in patients on steroids, -2.74 (95% confidence interval [CI], -2.77 to -2.70) compared with -2.65 (95% CI, -2.66 to -2.65) in those who had not received steroids. Our results fail to support the notion that the fracture threshold is altered in patients on long-term steroids and suggest that the same diagnostic criteria should be used for osteoporosis in patients whether or not they are taking corticosteroid therapy.