Sixty patients (39 females and 21 males) aged between 20 and 65 (average 48.5) with bipolar disorder in the depressive phase, according to the DSM III-R diagnostic criteria, were treated with fluoxetine (20-60 mg/die) for 8 weeks. Evaluation of therapeutical efficacy was performed at 0 time and after 14, 28, 42, and 56 days, using the following psychometric tests; HAM-D, SCL-90, CGI. At the end of treatment 42 patients (70%) showed a reduction of the HAM-D score over 50%. Clinical results suggest that fluoxetine is affective in bipolar disorder. Tolerability was judged good and very good in 76% of patients. Side effects were very mild and in any case of rapid regression.