Fibromyalgia syndrome (FMS) is a very prevalent disorder defined by the presence of hyperalgesia and allodynia that leads to musculoskeletal chronic pain very frequently associated with fatigue and a diversity of other symptoms. The cause of FMS is unknown and its pathogenesis is complex and not well understood. This paper will rather discuss central pain mechanisms and the role of stressors and other factors as triggering events for onset of clinical manifestations.