BACKGROUND: Epidural steroid injection (ESI) is one of the most common nonsurgical treatments for low back pain. In general, corticosteroid therapy often results in bone loss and osteoporosis. In previous studies, bone mineral density (BMD) was evaluated after epidural injections of relatively small numbers and relatively low total doses of corticosteroids. However, the relationship between BMD and multiple ESIs remains to be elucidated.