The case of a man who initially presented to an emergency room with an isolated dysarthria is reviewed in order to demonstrate how the history, clinical context, and clinical observations can lead to accurate or inaccurate diagnosis. The diagnostic process in this case illustrates (1) the value of experience in clinical practice; (2) the role of the history and clinical context in diagnosis, but their occasional capacity to mislead; (3) the importance of distinguishing evidence from inference; (4) the use of deductive strategies and pattern recognition in speech diagnosis; (5) the importance of diagnostic vigilance; (6) the value of distinguishing among dysarthria types; and (7) the contribution that the diagnosis of speech disorders can make to the localization and diagnosis of neurologic disease.