Depressive episodes are significant in bipolar illness since patients can spend up to one-third of their lives in depression. Although the treatment of bipolar depression remains an understudied area, new data from randomized, controlled trials and naturalistic studies have expanded the range of treatments available. The main aim in the treatment of bipolar depression is the prevention of the patient switching to mania and cycle acceleration, and antidepressant therapy may be contraindicated because of the risk for switching. Guidelines for the acute treatment of bipolar depression emphasize treatment with a mood stabilizer, of which lithium has been the most thoroughly studied in randomized, controlled trials in acute bipolar depression. Lamotrigine has also demonstrated significant efficacy in recent studies and has been approved by the FDA.