The recommended regimen of etidronic acid (disodium etidronate) for the treatment of Paget's disease of bone is 5mg/kg/day for a period of less than six months. There have, however, been reports of impaired mineralisation of bone and concern that the risk of fracture is increased with this dosage. We report a patient with Paget's disease in whom fractures occurred through pagetic and non-pagetic bone which appeared to be causally related to treatment with lose doses of etidronic acid. The osteomalacia resolved when etidronic acid was discontinued.