The objective is to evaluate the efficacy and safety of two doses of SSR149415 (250 mg and 100 mg twice daily) compared to placebo and escitalopram 10 mg once daily in outpatients with major depressive disorder.

Inclusion Criteria:

• Diagnosis of major depressive disorder, as defined by DSM-IV criteria and confirmed by the semi-structured MINI, recurrent episode.

Exclusion Criteria:

• Total score of less than 24 on the MADRS.
• HAM-D total score less than 18.
• Duration of the current depressive episode less than 1 month or greater than 2 years.
• Patients with a history or presence of bipolar disorders or psychotic disorders.
• Patients with alcohol dependence or abuse or substance dependence or abuse in the past 12 months except nicotine or caffeine dependence.
• Patients who have used the following prior to entry into Acute Phase: antipsychotics within 3 months, fluoxetine within 1 month, MAOIs within 2 weeks, other antidepressants, anxiolytics, or mood-stabilizer (lithium, anticonvulsants) within 1 week except as allowed in the protocol.

The investigator will evaluate whether there are other reasons why a patient may not participate