Objectives: This study was produced to examine the effects of moxibustion that had been played important role to traditional oriental medical treatment on disease. Recently, it was reported that moxi-tar which is generated in the process of moxibustion as burning combustibles decreased nitric oxide(NO) and inducible NO synthase (iNOS) generation in cellular experiments. Methods: Carrageenan-induced arthritis rat model was used to test the effect of moxi-tar as a chronic pain model. Diluted moxi-tar was single injected in several acupoints or combined with electroacupuncture (l ms, 2 Hz, and 2 mA) into contralateral ST36 acupoint for 30 min to assess the synergic effects. After the treatment, behavioral tests measuring stepping force were periodically conducted during the next 12 hours. Endogenous NO and iNOS, cyclooxygenase-2 (COX-2), and c-Fos protein expression in the spinal cord were examined on a rat model of carrageenan-induced arthritis. Results : After the induction of arthritis, rats subsequently showed a reduced stepping force of the affected limb for at least the next 4 days. The reduced stepping force of the limb was presumably due to a painful knee, since oral injection of indomethacin produced temporary improvement of weight bearing. Maxi-tar produced significant improvement of stepping force of the hindlimb affected by the arthritis lasting at least 9 hours. The magnitude of this improvement was equivalent to that obtained after an oral injection of 3 mg/kg of indomethacin and this improvement of stepping force was interpreted as an analgesic effect. Maxi-tar produced the improvement of stepping force of the affected hindlimb in a dose-dependent manner. Both NO production and iNOS, COX-2 protein expression increased by arthritis were suppressed by maxi-tar. Moxi-tar on combination with electroacupuncture (EA) produced more powerful and longer lasting improvement of stepping force of the hindlimb affected by the arthritis than either moxi-tar or EA did. Conclusion : The present study suggest that maxi-tar produces a potent analgesic effect on the chronic knee arthritis pain model in the rat and that moxi-tar-induced analgesia modulate endogenous NO through the suppression of iNOS/COX-2 protein expression.