A fair amount of research exists on acceptance and commitment therapy (ACT) as a model and a treatment for anxiety disorders and OCD spectrum disorders; this paper offers a quantitative account of this research. A meta-analysis is presented examining the relationship between psychological flexibility, measured by versions of the Acceptance and Action Questionnaire (AAQ and AAQ-II) and measures of anxiety. Meta-analytic results showed positive and significant relationships between the AAQ and general measures of anxiety as well as disorder specific measures. Additionally, all outcome data to date on ACT for anxiety and OCD spectrum disorders are reviewed, as are data on mediation and moderation within ACT. Preliminary meta-analytic results show that ACT is equally effective as manualized treatments such as cognitive behavioral therapy. Future directions and limitations of the research are discussed.