At present the majority of the treatment that is performed in the clinic is due to disease involving the pulp and periapical tissues. Dental pulp is a delicate connective tissue consisting of numerous blood vessels, lymphatic’s and nerves. The disease of the dental pulp occurring directly as sequelae of dental caries and pulp tissues can also infected by a retrograde infection, arising from the secondary canaliculi from the periodontal or from the apex during the course of periodontitis. This chapter discussed about etiological factors of pulp and periapical disease and their classification, clinical features, histopathological features and treatment with classical histopathology pictures and diagrammatic representation of sequelae of pulpit is.