Traditionally, the therapeutic approach to treatment-resistant depression (TRD) has relied on pharmacotherapy in various sequences and combinations, in addition to evidence-based psychotherapy or electroconvulsive therapy. Despite refinements to the existing therapeutic modalities, there remains a significant subpopulation of severely ill patients with refractory mood disorders who fail to achieve a clinical response despite aggressive psychosocial and biological treatments. Interest in the use of deep brain stimulation (DBS) for treatment-resistant psychiatric illness has emerged in recent years for a number of reasons: 1) as part of a general re-evaluation of both noninvasive and invasive brain stimulation techniques, 2) because of the demonstrated clinical efficacy of DBS for movement disorders, and 3) as a logical consequence of studies defining the functional neurocircuitry of several psychiatric disorders. This review will examine the progress of DBS in the treatment of Parkinson's disease and the potential implications for its use in TRD, as well as the role of the psychiatrist in selection and ongoing management of patients who receive this procedure.