Diffuse and chronic muscular pains, without any noticeable underlying anomaly, are a frequent cause for consultation. The origin of the pain was, at the beginning of the century, attributed to an inflammation of fascia, tendons, ligaments, subcutaneous tissues and even the muscle itself. Although this inflammatory etiology is not based on proven anatomical facts, some authors advocate an organic pathology of unknown origin and the terms of fibrositis or primary fibromuscular pain are used in the literature, especially the anglo-saxon literature, to describe such symptomatology. Clinical diagnostic criteria have been recently proposed in order to differentiate primary fibromuscular pain from functional diffuse muscular pains. The authors discuss the legitimacy of such distinction.