Multiple sclerosis (MS) is a chronic, inflammatory, and degenerative neurological illness with no cure. It has been suggested that Hyperbaric Oxygen Therapy (HBO(2)T) may slow or reverse the progress of the disease. This article summarizes the clinical evidence for the use of HBO(2)T in the treatment of MS. We conducted a literature review focused on the interaction of hyperbaric oxygenation and MS. In particular, we appraised the clinical data regarding treatment and performed a meta-analysis of the randomized evidence using the methodology of the Cochrane Collaboration. We found 12 randomized studies in the area, all of which were performed between 1983 and 1987. A meta-analysis of this evidence suggests there is no clinically significant benefit from the administration of HBO(2)T. The great majority of randomized trials investigated a course of 20 treatments at pressures between 1.75ATA and 2.5ATA daily for 60-120 min over 4 weeks against a placebo regimen. None have tested the efficacy of HBO(2)T against alternative current best practice. No plausible benefit of HBO(2)T on the clinical course of MS was identified in this review. It remains possible that HBO(2)T is effective in a subgroup of individuals not clearly identified in the trials to date, but any benefit is unlikely to be of great clinical significance. There is some case for further human trials in selected subgroups and for prolonged courses of HBO(2)T at modest pressures, but the case is not strong. At this time, the routine treatment of MS with HBO(2)T is not recommended.