The efficacy of cognitive-behavioral therapy (CBT) for anxiety in adults is well established. In the present study, the authors examined whether CBT tested under well-controlled conditions generalizes to less-controlled, real-world circumstances. Fifty-six effectiveness studies of CBT for adult anxiety disorders were located and synthesized. Meta-analytic effect sizes are presented for disorder-specific symptom measures as well as symptoms of generalized anxiety and depression for each disorder, and benchmarked to results from randomized controlled trials. All pretest-posttest effect sizes for disorder-specific symptom measures were large, suggesting that CBT for adult anxiety disorders is effective in clinically representative conditions. Six studies included a control group, and between-groups comparisons yielded large effect sizes for disorder-specific symptoms in favor of CBT. Benchmarking indicated that results from effectiveness studies were in the range of those obtained in selected efficacy trials. To test whether studies that are more representative of clinical settings have smaller effect sizes, the authors coded studies for 9 criteria for clinical representativeness. Results indicate an inverse relationship between clinical representativeness and outcome, but the magnitude of the relationship is quite small.