In spite of the fact that suicidal behaviour is very complex, multicausal human behaviour, untreated current major Axis I affective disorder (bipolar and unipolar major depressive episode: 56-87%) is the most powerful predictor of suicide, particularly in the case of prior suicide attempt. Prospective and retrospective follow-up studies clearly support the eivedent clinical observation that if patients with unipolar or bipolar mood disorder committ or attempt suicide, they do it mostly during the major depressive episode (78-89%) and less frequently in dysphoric mania or mixed affective episode (11-20%) but very rearly during euphoric mania or euthymia, indicating that suicidal behaviour in mood disorder patients is a state-dependent phenomenon. Consequently, effective treatment of acute major mood episodes and successful long-term management is very important part of suicide prevention of patients with affective disorders. Indeed, it has been repeatedly demonstrated that long-term lithium treatment of bipolar disorder and unipolar depression reduces the risk of completed and attempted suicide markedly, even in this high-risk population. The marked anti-suicidal potential of lithium seems to be more than the simple reflexion of its phase-prophylactic effect, as it has been demonstrated that during the long-term prophylaxis of recurrent unipolar and bipolar affective disorder patients with at least one prior suicide attempt, a significant reduction in the number of suicide attempts was found not only in the excellent responders (93%), but also in moderate responders (83%) and in poor responders (49%).