This paper will discuss different definitions of the term "mood stabilizer" and highlight in detail the antiepileptic drugs carbamazepine, valproate and lamotrigine with respect to their relative strengths in stabilizing mood in bipolar patients. These drugs are heterogeneous in their mechanisms of action and in their efficacy to stabilize patients with epilepsy and the various mood states in bipolar disorder. Lamotrigine has obtained approval in several countries for the indication of preventing bipolar depressive episodes, which raises the question of differential efficacy of other antiepileptic drugs as mood stabilizers in the prevention of either depressive or hypo-/manic episodes. A Medline Search to 2006 was conducted for controlled acute and maintenance studies of the three scientifically and clinically most established antiepileptic drugs carbamazepine, valproate and lamotrigine. The medications discussed in this review only partly fulfill definitions of a mood stabilizer, and we suggest that future research should focus on combined treatment strategies.