During psychosis evolution, depressions occur frequently with a prevalence between 10% and 70% (average 25%-50%). Depression aggravates psychosis prognosis by increasing the risk of suicide, relapse and hospitalization. So antidepressant and neuroleptic treatments are often associated. Many studies with contradictory results were realized. Some concluded a favourable effect of this association, others considered this concomitant medication aggravates psychotic symptoms and adverse reactions. However this association appears to be efficient especially in deficitary or depressive forms of schizophrenia. The objective of this multicentre, non comparative, open study is to assess during 6 weeks the efficacy and tolerability of dothiepin in the treatment of depression occurring during the evolution of psychosis. The initial score on HDRS (17 items) had to be at least 18. 124 patients (40.7 years, 63.1% male) suffering from chronic psychosis associated with depressive syndrome were included in 29 hospital centres. According to DSM III-R criteria, 71.9% of patients were schizophrenic and 43% were suffering from major depressive illness. 16 patients (12.9%) stopped prematurely the treatment and side effects were reported for 8 of them. Any unexpected side effect occurred and pre-existing psychotic disorders reappeared for one patient. During the whole study, 63% of the population were treated with 75 mg as daily dosage of dothiepin. All concomitant treatments except antidepressant were authorized. 115 patients (95%) received at least one associated neuroleptic treatment and 54 patients (44.6%) a concomitant antiparkinsonian treatment. The significant decrease, between day 0 and day 45, of the global score on HDRS (from 23.78 to 8.48, p < 0.01), confirms the improvement of depression.(ABSTRACT TRUNCATED AT 250 WORDS)