We sought to determine whether HBOT leads to parental reported behavioral changes and alterations in cytokines in children with ASD. Ten children completed 80 sessions of HBOT and all improved by 2 points on the clinician-rated CGI-I scale (much improved) as well as several parent-completed measures of behavior. The lack of a control group limits the ability to determine if improvements were related to HBOT. Enrolled children did not exhibit abnormal cytokine levels at baseline and no significant changes in mean cytokine levels were observed. Although this study was limited by the small sample size and by the variable nature of cytokines, we found no evidence that HBOT affects cytokine levels or that cytokine levels were associated with behavioral changes.