By using spectrofluorophotometry, it was observed that electroacupuntrure at "Huantiao" points of rat could decease the content of 5-hydroxytryptamine (5-HT) and increase the content of 5-hydroxyindoleacetic acid (5-HIAA) in spinal cord. However, the above effects of electroacupunture were obviously reduced after the C fibers of rats had been destroyed by capsaicin, which suggesting that capsaicin-sensitive C fiber might take part in the roles of electroacupuncture's promoting the release and utilization of 5-HT in spinal cord.