OBJECTIVE: The purpose of this study is to find out what is the effect of epidural corticosteroid injection on bone metabolism. METHOD: We have assessed the systemic effects of a single epidural triamcinolone acetonide injection on biochemical indices of bone formation and resorption in patients with lumbosacral radiculopathy. Twenty patients who had lumbosacral radiculopathy and free from exposure to corticosteroid for at least 6 weeks were selected for this study. Patients were classifed as two groups; 1) epidural block with 2% lidocaine 3 ml and 0.9% normal saline 15 ml (4 men, 5 women; mean age 47.2+/-7.6 years) and 2) combination of triamcinolone acetonide 40 mg (5 men, 6 women; mean age 49.6+/-8.2 years). Fasting serum and the second voided urine were collected at 0, 1, 3, 7 and 14 days after the single epidural injection for bone-related biochemicalmarkers measurements. RESULTS: 1) Level of serum osteocalcin showed a significant time trend in the epidural corticosteroid injection group. Osteocalcin decreased dramatically from 11.2+/-3.4 ng/ml on day 0 to 5.9+/-2.8 ng/ml on day 1, 6.1+/-1.5 ng/ml on day 3 (p<0.05). After the initial drop, the level recovered to 9.8+/-3.7 ng/ml by day 7, and returned to preinjection level on day 14, at 10.9+/-4.1. 2) Urinary deoxypyridinoline levels did not show any significant changes. CONCLUSION: According to the above results, the epidural injection of corticosteroid may be a better therapeutic mode, with less potential for harmful effects to bone metabolism, in providing effective relief of symptoms to patients with lumbosacral radiculopaties.