To determine whether hyperbaric oxygen (HBO2) therapy should be used for the treatment of autism spectrum disorders (ASD). A literature search was performed on PubMed, Cochrane Library and DynaMed for studies evaluating the use of HBO2 for ASD treatment. The studies were then reviewed for the highest quality evidence. The evidence is weak for the use of HBO2 in ASD, with only one, likely flawed, randomized control study showing treatment benefit. HBO2 should not be recommended for ASD treatment until more conclusive favorable results and long-term outcomes are demonstrated from well-designed controlled trials.