Turkish researchers conducted an RCT to evaluate the effect of hyperbaric oxygen (HBO) therapy in fibromyalgia syndrome. Tender points and pain threshold were assessed before and after the first and 15th sessions of therapy. Pain was also scored on a VAS. There was a significant reduction in tender points and VAS scores and a significant increase in pain threshold of the HBO group after the first and 15th therapy sessions. There was also a significant difference between the HBO and control groups for all parameters except the VAS scores after the first session.