To compare the efficacy and safety of a select serotonin re-uptake inhibitor (SSRI, sertraline) and a tricyclic antidepressant (TCA, nortriptyline) in outpatients over the age of 60 who meet Diagnostic and Statistical Manuel-IV criteria for unipolar major depression, excluding patients who meet criteria for psychotic or atypical subtype. To test the hypothesis that medication condition interacts with diagnostic subtype (melancholic vs non-melancholic) in determining antidepressant response. To examine the roles of symptom severity and alternative diagnostic subtyping in contributing to this pattern.