Fibromyalgia is a noninflammatory rheumatic disorder characterized by chronic widespread musculoskeletal pain. Although many studies have described the pain and other clinical symptoms associated with this disorder, the primary mechanisms underlying the etiology of fibromyalgia remain elusive. This article reviews recent data supporting the links among each of three systems--the musculoskeletal system, the neuroendocrine system, and the central nervous system (CNS), all of which appear to play major roles in fibromyalgia pathophysiology--and pain in fibromyalgia, and concludes by presenting a model of the pathophysiology of abnormal pain perception in fibromyalgia which integrates the research findings described.