Medically unexplained symptoms are a source of frustration for clinician and patient alike. They simultaneously test the credibility of the doctor and the patient; the former, for his or her inability to label the patient's complaint, and the latter, for the ignominy of being perceived to have a factitious symptom. This review explores the discursive construction of such symptoms in the medical literature in order to appreciate the context in which medicine understands and manages non-diagnosed complaints. It uses medically unexplained symptoms as a heuristic for understanding the role of classification in constituting medicine as a social authority. In the absence of diagnostic category, medically unexplained symptoms are recast as a discrete category of their own. However, this category implies the infallibility of the physician and the relevance of the medical model in all circumstances. It transfers responsibility for the disorder to the patient in a way that may hinder resolution, and it ignores socio-historical practices that influence when and why patients consult a physician.