Patients with fibromyalgia (FM) frequently have gastrointestinal symptoms and signs. This article critically reviews the available literature and concludes the following: evidence that inflammatory bowel disease is associated with FM is contradictory, but should be looked for in patients taking concomitant steroids; patients diagnosed with celiac disease often have a history of FM or irritable bowel syndrome (IBS) that may or may not be present; reflux, nonulcer dyspepsia, and noncardiac chest pain are common in FM patients; medications used to manage pain, inflammation, and gastrointestinal complaints confound the management of FM; and IBS affects smooth muscles and the parasympathetic nervous system, while FM patients have complaints of striated muscles and dysfunction of the sympathetic nervous system. Of those patients with FM, 30% to 70% have concurrent IBS. Small intestinal bacterial overgrowth is associated with hyperalgesia and IBS-like complaints, is common in FM, and responds transiently to antimicrobial therapy.