Objectives : In this study, we investigated the effect and pathway of contralateral heterotropic electroacupuncture (EA) on pain induced by fonualin in rats. Methods : Acu-points in the right forepaws, HT 7 and PC 7 were stimulated with 3~4mA, 2ms, and 10Hz after 5% formalin (50ul) s.c. injection to the left hind paw. In addition, it was investigated whether the dorsolateral funiculus (DLF), known to be related the descending inhibition, mediates analgesic effects of the contralateral heterotropic EA or whether administration of naltrexone, an opioid antagonist, blocks the effect of EA. Results : The results showed that contralateral heterotropic electroacupuncture (EA) inhibited late phase (63.311.7%) of pain induced by fonualin in the behavioral test, but sham-EA had little effect on pain behavior (85.616.8%) and no analgesic effects after transection of the dorsolateral funiculus (95.718.7%). The pretreatment of naltrexone (10mg/kg, i.p.) could not inhibit the analgesic effects of EA on formalin-induced pain behavior (70.713.1%). Also,EA suppressed formalin injection induced expression of cFos like protein (cFL) in the dorsal homo but not sham-EA. Suppressed expressions of cFL in the spinal cord were eliminated after transection of the ipsilateral dorsolateral funiculus at T10-11 leve1s. However, pretreatment of naltrexone could not prevent the suppressive expressions of cFL at the spinal cord. Conclusions : These results suggest that the analgesic effect of contralateral heterotropic electroacupuncture may be modulated through the dorsolateral funiculus constituting the descending inhibition.