Depressive symptoms are highly prevalent in patients with epilepsy. The antiepileptic drug lamotrigine has been shown to be an effective treatment for the depressive phase of bipolar disorder and to enhance mood and well-being in epilepsy patients. The effects of lamotrigine monotherapy on depressive symptoms in epilepsy have not been evaluated to date in a controlled clinical trial. A recently completed double-blind epilepsy trial comparing the effects of lamotrigine monotherapy and valproate monotherapy on weight change incorporated a battery of standard mood assessments. Mean screening Beck Depression Inventory scores showed that both lamotrigine and valproate groups suffered from mild depression at baseline. Lamotrigine monotherapy was reliably associated with earlier and larger improvements than valproate in mood assessed with the Beck Depression Inventory, the Cornell Dysthymia Rating Scale, and the Profile of Mood States. Considered in the context of other data showing lamotrigine's antidepressant efficacy in bipolar depression, these results suggest that lamotrigine improves mood in mildly depressed patients with epilepsy. Lamotrigine may be particularly useful in treating epilepsy patients with comorbid depression, the most common psychiatric illness in epilepsy.