Epidemiological studies point to systematic increase of the incidence of depression in most countries. The prevalence of depression in various somatic and neurological diseases is several-fold higher than in general population. In the treatment of depression, the most important is prudent administration af antidepressant drugs and management of treatment-resistant depression. Introduction of new diagnostic instruments has made possible better diagnosis of bipolar affective illness. The progress in treatment of bipolar affective illness means systematic update of therapeutic procedures on different stages of the illness (mania, depression, prevention of recurrences) with appropriate use of mood-stabilizing drugs. First generation mood-stabilizing drugs include lithium, valproates and carbamazepine while those of second generation, atypical neuroleptics and lamotrigine.