Fibromyalgia Syndrome(FMS) is a persistent and debilitating disorder estimated to impair thequalityoflifeof2-4% of the population, with 9:1 female-to-male incidence ratio. FMS is an important representative example of central nervous system sensitization an disassociated with abnormal brain activity. Key symptoms include chronic widespread pain, allodynia and diffuse tenderness, along with fatigue and sleep disturbance. The syndrome is still elusive and refractory. The goal of this study was to evaluate the effect of hyperbaric oxygen therapy(HBOT) on symptoms and brain activity in FMS.