Before the rise of atypical antipsychotics, lithium used to be the most frequently investigated substance in the acute treatment of bipolar disorders, although studies are not always of the highest methodological standard. Due to the doubt about a sufficient efficacy of lithium expressed in recent years from various sides, and the simultaneous availability of newer treatment alternatives, this paper attempts to make a critical stocktaking of our knowledge about lithium in the acute treatment of bipolar disorders. Aspects concerning the changed disorder concept through the broadening of the bipolar spectrum, together with the available results from controlled and open studies with lithium, are presented and appraised. This shows that lithium should still be seen as an essential, but not the only corner stone in the differentiated treatment of bipolar patients. Provided that it is taken reliably and well-tolerated, lithium represents a first choice treatment, particularly for a classical course of manic-depressive illness (Bipolar I disorder), especially for mild to moderate manic syndromes.However, as antidepressive treatment, lithium should rather not be applied as a monotherapy, particularly in severe bipolar depression, since with the new generation of antidepressants and anticonvulsants well-tolerated and very effective alternatives are available. In combination treatment, lithium should be applied particularly when it has already shown good prophylactic efficacy and/or in patients for whom a high suicide risk must be presumed.