Tongue Diagnosis is a diagnostic tool that is so important and pervasive in contemporary training and practice that it is usually considered and presented as if it had always been so. Diagrammatic and theoretical detail in Chinese medical textbooks give the impression that, as a system, tongue diagnosis has achieved a parity with pulse reading as a cornerstone of the contemporary clinical encounter. And yet, even a cursory look at a selection of classical texts, case histories and formularies from the Han to the Ming dynasty suggests that tongue diagnosis has not always enjoyed its current status. While the tongue is mentioned as an indicator of health or illness in classical texts, the privileging of the tongue in diagnosis is relatively recent. This article presents a preliminary survey of tongue diagnosis in Chinese medicine and offers some hypotheses about the process through which inspection of the tongue transformed from incidental observations to become a pillar of diagnosis. At the same time it is a practitioner̓s account and stands as a personal reflection on the value and relevance of engaging in history for practitioners of traditional medicines.