Transcranial magnetic stimulation (TMS) therapy has proven to lead to symptom improvement in many individuals with major depressive disorder (MDD), yet there is heterogeneity in outcome, with some patients showing robust remission and other showing minimal symptom change. Identifying which individuals are likely to benefit from TMS therapy early in the course of treatment would support continued treatment for those predicted to do well, and consideration of alternative treatments for others individuals. This study will test specific hypotheses about the relationships between early neurophysiologic changes and later clinical outcome with TMS treatment.