This study was designed to investigate the effect of the endogenous beta-carboline, harmane, on neuropathic pain produced by chronic constriction injury (CCI) of the sciatic nerve. Thermal allodynia evaluations were made preoperatively, postoperatively on the fifteenth day, and after harmane administration. Harmane (1, 2.5, 5, 10, or 20 mg/kg) was administered intraperitoneally for 5 days beginning from postoperative day 15. Treatment with harmane had a profound anti-allodynic effect in a dose-dependent manner. In conclusion, harmane might provide a new approach to treatment of neuropathic pain.