Sertraline vs. Venlafaxine XR

Inclusion Criteria: * Single or Recurrent Episode of MDD without psychotic features * Additional diagnoses will be permitted only if they are identified as secondary diagnoses * 18 or above on 17-item Ham-D with item 1 (depressed mood) score of 2 or above Exclusion Criteria: * Current or past diagnosis of Bipolar Disorder * Any history or current psychotic disorder * Current psychotic symptoms, including current delusional depression * Current diagnosis of delirium or dementia * Alcohol or drug abuse or dependence in last 6 months or currently * Schizoid, Schizotypal, or Borderline Personality Disorder * Non-response to sertraline at least 150mg for 4 weeks or more, venlafaxine XR at least 225mg for 4 weeks or more, or non-response to 2 antidepressants in the current episode * Use of any antidepressant within 2 weeks of baseline (4 weeks for fluoxetine) * Use of herbal and/or homeopathic remedies concomitantly or within 2 weeks of baseline excluding vitamins and mineral supplements * Use within 1 week of baseline or concomitant use of any psychotropics with the exception zolpidem or zopiclone PRN for sleep * Use within 4 weeks of baseline of benzodiazepines taken on a regular, daily basis (PRN use is acceptable as long as none in week leading up to randomization) * Score of 3 or 4 on the suicide item, item 3 of the Ham-D scale at screen or baseline visit * Participation in any other studies concomitantly or within 90 days prior to entry into this study * Treatment with monoamine oxidase inhibitors within 14 days of baseline * Treatment of electroconvulsive therapy within 30 days of baseline * Previous history or intolerance or hypersensitivity and/or venlafaxine XR * Likelihood of requiring treatment during the study period with drugs not permitted by the study protocol * Presence of serious and/or unstable medical condition * Abnormal laboratory results * Positive pregnancy test and/or nursing women or fertile women not practicing an effective method of birth control * History seizure disorder-excluding febrile seizures of childhood * Any other condition which in the investigator's judgement might increase the risk to the subject or decrease the chance of obtaining satisfactory data * Mental condition rendering the subject unable to understand the procedures * Unable and/or unlikely to comprehend and/or follow the protocol