Mindfulness-based stress reduction (MBSR) has been reported to reduce anxiety in a broad range of clinical populations. However, its efficacy in alleviating core symptoms of specific anxiety disorders is not well established. We conducted a randomized trial to evaluate how well MBSR compared to a first-line psychological intervention for social anxiety disorder (SAD). Fifty-three patients with DSM-IV generalized SAD were randomized to an 8-week course of MBSR or 12 weekly sessions of cognitive-behavioral group therapy (CBGT). Although patients in both treatment groups improved, patients receiving CBGT had significantly lower scores on clinician- and patient-rated measures of social anxiety. Response and remission rates were also significantly greater with CBGT. Both interventions were comparable in improving mood, functionality and quality of life. The results confirm that CBGT is the treatment of choice of generalized SAD and suggest that MBSR may have some benefit in the treatment of generalized SAD.