The authors expressed in 1984 the assumption that lithium is the drug of the phenomenon of suicidal action in affective disorders. In the present paper the authors describe in a group of 56 patients with affective disorders in the course of lithioprophylaxis a marked decline of the suicide rate at the 4% level of significance. Therefore the authors are still in favour of the view that lithium is the drug in suicidal behaviour in affective disorders. This mechanism can be explained by the antiaggressive as well as prophylactic action of lithium. In the authors' opinion it is possible that the mechanism of this action may be conditioned by the interference of lithium with the dysfunction of the central serotonergic system.