The objective of this study was to evaluate the long-term safety of desvenlafaxine for continuation treatment of major depressive disorder (MDD) in Japanese patients. This was a phase 3, multicenter, 10-month, open-label study with flexible dosing of desvenlafaxine (25, 50, 100 mg/day). Japanese patients with MDD who had completed an 8-week, double-blind, placebo-controlled study in which patients received 25 or 50 mg/day desvenlafaxine or placebo were enrolled. In this study, patients received desvenlafaxine 25 mg/day from days 1 to 14, with subsequent upward titration, to a maximum of 100 mg/day, determined by clinical response. Of 304 patients, 75 (24.7%) discontinued during the on-therapy period; patient request was the most common reason (11.5%). Treatment-emergent adverse events were reported by 240 patients (78.9%) during the on-therapy period; the most common adverse events were nasopharyngitis (37.2%), somnolence (11.5%), headache (10.5%), and nausea (10.2%). For the ITT-LOCF population, the mean change from baseline in the 17-item Hamilton Rating Scale for Depression (HAM-D₁₇) total score was -4.76 (95% confidence interval: -5.47 to -4.05); continued numerical improvements in the HAM-D₁₇ total scores and other depression outcome measures were observed irrespective of treatment in the previous study. Long-term use of desvenlafaxine was safe and well tolerated, with a clinical benefit/risk profile similar to that in other populations.