A sample of 855 rural adult inhabitants of Udmurtia was interviewed by means of the Composite International Diagnostic Interview (CIDI) in order to investigate the incidence and prevalence of mood disorders. Depression affected 30.5% of the population according to ICD-10, and 22% according to DSM-III-R over a 12-month period. Depressive disorders were more common in women (40.5%) than in men (17.4%), and in subjects who were widowed (68.8%), divorced (55.6%) or had poor family relationships. Depression was not related to ethnicity, educational level, income or living conditions. Depression showed a high level of comorbidity with social phobia in Udmurts and with persistent somatoform pain disorder in Russian women. The annual incidence of depressive episode was 7.5%, and the highest risk of depression was among younger women and older men.