BACKGROUND: Studies on individual psychotherapy indicate that some interventions may reduce the number of recurrences in bipolar patients. However, there has been a lack of structured, well-designed, blinded, controlled studies demonstrating the efficacy of group psychoeducation to prevent recurrences in patients with bipolar I and II disorder. METHODS: One hundred twenty bipolar I and II outpatients in remission (Young Mania Rating Scale score <6, Hamilton Depression Rating Scale-17 score <8) for at least 6 months prior to inclusion in the study, who were receiving standard pharmacologic treatment, were included in a controlled trial. Subjects were matched for age and sex and randomized to receive, in addition to standard psychiatric care, 21 sessions of group psychoeducation or 21 sessions of nonstructured group meetings. Subjects were assessed monthly during the 21-week treatment period and throughout the 2-year follow-up. RESULTS: Group psychoeducation significantly reduced the number of relapsed patients and the number of recurrences per patient, and increased the time to depressive, manic, hypomanic, and mixed recurrences. The number and length of hospitalizations per patient were also lower in patients who received psychoeducation. CONCLUSION: Group psychoeducation is an efficacious intervention to prevent recurrence in pharmacologically treated patients with bipolar I and II disorder.