The goal of a classification system of medical conditions is to facilitate accurate communication, to ensure that each condition is described uniformly and universally and that all data banks for the storage and retrieval of research and clinical data related to the conditions are consistent. Classification entails deciding which kinds of diagnostic entities should be recognized and how to order them in a meaningful way. Currently there are 3 major pain classification systems of relevance to orofacial pain: The International Association for the Study of Pain classification system, the International Headache Society classification system, and the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). All use different methodologies, and only the RDC/TMD take into account social and psychologic factors in the classification of conditions. Classification systems need to be reliable, valid, comprehensive, generalizable, and flexible, and they need to be tested using consensus views of experts as well as the available literature. There is an urgent need for a robust classification system for neuropathic trigeminal pain. Keywords: classification, pain