A Consensus Conference on Terminology was convened by the American Association of Endodontists in Chicago on Oct 3, 2008 to review solicited papers on focused questions. This paper addressed the question: Identify and determine the metrics, hierarchy, and predictive value of all the parameters and/or methods used during endodontic diagnosis. The best available clinical evidence was used to determine the sensitivity, specificity, and predictive value of pulpal and periapical testing methods and imaging technologies. Diagnosis of dental pulp diseases suffers from operator's inability to test/image that tissue directly due to its location within dentin. In general, current pulp tests are more valid in determining teeth that are free of disease, but less effective in identifying teeth with pulp disease. Radiographic imaging is probably the most commonly used diagnostic tool to determine the status of root-supporting tissue, although interpretation of structural changes in the periradicular tissues is still considered unreliable.