The most commonly used clinical signs of root caries are visual (color, contour, surface cavitation) and tactile (surface texture) descriptions of a lesion. The traditional methods of visual-tactile diagnosis for root caries can produce a correct diagnosis but usually not until the lesion is at an advanced stage. Despite the subjectivity inherent in interpreting the clinical signs of root caries diagnosis, good to excellent inter-examiner reliability has been reported in clinical studies; however, the presence of filled surfaces dramatically enhances the agreement. When only untreated root caries is diagnosed, examiner reliability is reduced considerably. Clinicians look to diagnostic tests in the hope that they will perform better (that is, be more reliable) than clinical diagnosis and, therefore, can be used to replace clinical diagnosis. From the limited data available on diagnostic tests for root caries, tests determining the presence or absence of mutans streptococci and Lactobacilli are the most clinically helpful, producing calibrated efficiency scores exceeding 40 percent. The risk assessment approach to root caries diagnosis involves the determination of a patient's risk through the interpretation of clinical signs and the selection and application of an appropriate diagnostic test if the clinician is unsure of the diagnosis.