In contrast to its widespread use in the prophylaxis of affective illness and in the acute treatment of mania lithium has not well been established in the treatment of acute depressive disorders. However, recent results from placebo controlled trials on lithium augmentation have shown its efficacy in the treatment of depressive disorders. Three different modes of application of lithium have been investigated since the 1960s and are reviewed in this article: 1. Although not a first line antidepressant lithium can be applied in monotherapy in the treatment of mild depressive episodes particularly in bipolar patients. 2. The successful additional use of lithium in patients not responding to conventional antidepressive treatment (lithium augmentation) has repeatedly been shown in controlled clinical trials since the 1980s. Therefore, lithium augmentation therapy has been established as treatment option of first choice in refractory depression. 3. Up to now there is little data concerning the initial combination of lithium with a conventional antidepressive drug: this indication of lithium seems to be useful in the treatment of depressive episodes in bipolar patients with a history of switching into mania during administration of tricyclics and leading to faster symptom relief.