Pulp and periodontium belong to two different tissues, but their relationship is dynamic, the communication between the pulp and the periodontium may through (1) apical foramen, (2) lateral canal, (3) dentinal tubules. Pulpal disease may induce the destruction of periodontium, also, periodontal disease may induce the degeneration of pulp. The treatment of endodontic-periodontic lesion depend on a precise diagnosis, and the treatment sequence is primary endodontic therapy and secondary periodontal therapy.