Teeth with both endodontic and periodontal diseases have often been considered to have a very poor prognosis. However, this is largely due to a poor understanding of the disease processes which in turn is a result of confusing classifications of these diseases. A further compounding problem in most journal articles and textbook chapters on this topic has been the inclusion of all possible conditions that can affect both the periodontium and the pulp or root canal system at the same time even though these conditions are conditions in their own right – for example, a root perforation, root fracture, invasive resorption, etc. In this lecture, an alternate classification will be presented. This classification is based on the individual diseases that are present, rather than attempting to combine them, with the concept that there are two separate diseases occurring on the same tooth at the same time. This classification can then be used to determine the best way to manage the tooth. A particular sequence and approach to treatment will be outlined to help improve the prognosis of teeth with concurrent endodontic and periodontal diseases.