One randomized controlled trial with a crossover active comparator and one prospective non-randomized cohort study formed the evidence base for this review. The RCT provided evidence to suggest that two months of hyperbaric oxygen therapy (HBOT) increases pain thresholds, physical functionality, and health-related quality of life, while decreasing tender points and psychological distress in female patients with Fibromyalgia Syndrome (FMS) at three months post-treatment. In addition, according to single photon emission computed tomography analyses, the majority of patients were classified as responders to HBOT and were assessed as having beneficial changes in brain activity within the specific regions of the brain known to be previously associated with abnormal activity in patients with FMS. However, the generalizability of HBOT to the Canadian population and in the male population with FMS remains uncertain.The prospective preliminary non-randomized study identified provided evidence to suggest that two weeks of hyperbaric oxygen therapy increased pain thresholds and health-related quality of life and decreased disability in patients with myofascial pain syndrome (MPS) at three months post-treatment. However, the generalizability of HBOT to the Canadian population with MPS is unclear as is its long-term effectiveness.No evidence was identified regarding the cost-effectiveness of HBOT for the treatment of chronic musculoskeletal pain.