 Inclusion criteria: 1. Males or females, 18 years of age or more; 2. Outpatients; 3. Major depressive disorder based on DSM-IV criteria, withwithout current co-morbid anxiety disorder; 4. Has two or more episodes of depression including the current episode in the past 5 years, with an interval of at lease 2 months between the end of the previous episode and the beginning of the current episode. 5. The baseline score of 17-item Hamilton Rating Scale for Depression HAM-D17; 6 If female of childbearing potential, have a negative urine pregnancy test at baseline, if appropriate, and use a medically acceptable method of contraception throughout the study. 