Bipolar disorder is a common and often chronic and debilitating mental illness. The depressive phase of bipolar disorder contributes the largest portion of the disorder, and treatment resistant bipolar depression represents a significant public health problem. Recent research has suggested that bipolar depression is associated with elevated brain glutamate activity. We hypothesize that riluzole, a drug approved for ALS which inhibits glutamate activity, will lead to clinical improvement in patients with bipolar depression.