Ninety-six patients with bipolar disorder who attended a lithium clinic were reviewed in a retrospective study. Sleep disorders were studied in 85 depressive episodes. Eighty-one percent of the subjects presented with insomnia; the mixed type being the most frequent (49%) followed by early awakening (25%). The evolution of depression in the patients was compared according to the treatment received for insomnia: sedative antidepressants vs other anxiolytic or hypnotic drugs. Fifteen percent of patients shifted to mania, this group more frequently receiving sedative antidepressants (p < 0.05). Moreover, the patients who had received sedative antidepressants as therapy for insomnia (N = 61) showed a tendency to have a shorter asymptomatic interval before the following relapse (13 months vs 19 months; p = 0.06). In view of these results, we consider that the use of sedative antidepressants as a treatment for insomnia during depressive episodes in bipolar patients could be a factor contributing to worse prognoses; in these cases it appears that the use of other hypnotic drugs would be more advisable.