The primary objective is to evaluate the long-term safety of desvenlafaxine succinate sustained-release (DVS SR) during open-label treatment in adult outpatients with fibromyalgia syndrome.

Patients completing study 3151A4-327 have the opportunity to be treated with DVS SR during the 6 month extension study.

Inclusion Criteria:

• Outpatients who have completed double-blind treatment in study 3151A4-327 for fibromyalgia Syndrome with no major protocol violations and no events that would preclude the patient's entry into the long-term open-label study.
• Women of childbearing potential must have a negative serum pregnancy test result at study start.

Exclusion criteria:

• Presence of any new/and or clinically important medical condition that might compromise patient's safety.
• Use of prohibited treatment.
• Meets any of the exclusion criteria listed for study 3151A4-327.