Previous research has established efficacy of cognitive behavioral therapy (CBT) for anxiety disorders, yet it has not been widely assessed in routine community clinic practices. Efficacy research sacrifices external validity to achieve maximum internal validity. Recently, effectiveness research has been advocated as more ecologically valid for assessing routine clinical work in community clinics. Furthermore, there is a lack of effectiveness research in group CBT. This study aims to extend existing research on the effectiveness of CBT from individual therapy into group therapy delivery. It aimed also to examine outcome using not only symptom measures, but also measures of related symptoms, cognitions, and life quality and satisfaction. Results from a cohort of patients with various anxiety disorders demonstrated that treatment was effective in reducing anxiety symptoms to an extent comparable with other effectiveness studies. Despite this, only 43% of individuals showed reliable change, and 17% were 'recovered' from their anxiety symptoms, and the post-treatment measures were still significantly different from the level of anxiety symptoms observed in the general population.