Bipolar disorder is a severe, chronic, and often life-threatening illness. Despite the availability of a wide range of antidepressant drugs, a proportion of patients fail to respond to first-line antidepressant treatment despite adequate dosage, duration, and compliance. Studies suggest that the glutamatergic system may play a role in the pathophysiology and treatment of depression. Felbamate and other agents which reduce glutamatergic neurotransmission may represent a novel class of antidepressants.