Purpose: This article reviews the literature on the anatomy and the role of the implant-mucosal interface in the long-term success of oral endosseous implants. Materials and Methods: In vitro, in vivo animal, and in vivo human studies are reviewed and discussed. Results: The anatomy of the implant-mucosal interface is described. The interface shares many features with periodontal mucosa. A clinically healthy implant-mucosal interface is a routine and predictable occurrence. The validity of using traditional clinical periodontal parameters to indicate or predict changes in peri-implant marginal bone height is unproven, especially if inflamed mucosal tissues are present. Conclusion: In general, the human host response of peri-implant mucosa to long-term functional challenges if favorable.