Objective: Recent studies suggest that, when combined with pharmacotherapy, structured psychotherapy may modify the course of bipolar disorder. However, there are few studies that have examined the effects of cognitive behavioral group therapy on the course of this disorder.The aim of the present study was to evaluate the effectiveness of 14 sessions of cognitive behavioral group therapy, combined with pharmacotherapy, on the treatment of patients with bipolar disorder, and to compare our results against those from the use of pharmacotherapy alone. Method: Forty-one patients with bipolar I and II disorder participated in the study and were randomly allocated to one of two treatment groups; thirty-seven patients remained in the study until its completion. Mood and anxiety symptoms were measured in all subjects. Statistical analysis was used to investigate if the groups differed with respect to demographic characteristics and the scores recorded in the pre-and post-treatment stages, as well as during treatment (intra/inter groups