Cognitive-behavioral therapy (CBT) is known to be effective for a number of disorders, and can be delivered effectively by trainees in controlled settings. However, the effectiveness of trainee therapists in general practice compared to that of more experienced therapists is unknown. In this study, the authors used a benchmarking strategy to compare the outcomes of naturalistic CBT delivered by trainee therapists to those of efficacy and effectiveness studies using primarily professional therapists. Patients (N = 249) with mood and anxiety disorders were treated by trainees (primarily by interns and postdocs) using nonstandardized nonmanualized CBT at an outpatient clinic in an urban academic medical center. Changes in anxiety and depression were assessed using effect sizes, reliable and clinically significant change, and benchmarked to efficacy and effectiveness studies. Symptoms of anxiety and depression significantly improved from start to end of treatment. Rates of improvement and recovery compared favorably to those achieved in other studies, with the exception of recovery rates in severe depression. Effect sizes were in the medium to large range, but generally lower than those achieved in other studies. Results suggest that CBT can be delivered effectively by trainees in an outpatient setting. (Contains 5 tables.)