Abstract: Although average measurements of the biologic zone do not necessarily reflect any one clinical situation, they do establish a basis upon which clinical decisions can be made. Clinical impressions, human autopsy material, and animal studies support the concept of a biologic width. Impingement on the attachment in a susceptible host has shown adverse reactions, including gingival inflammation and alveolar bone loss. The concept is clinically important in determining the extent of osseous surgery necessary in the exposure of sound tooth structure. If the implant-abutment interface is considered to be similar to a subgingival crown margin, its importance in relation to peri-implant inflammatory disease is readily apparent. In the presence of inflammation, it is likely that epithelial migration would occur to a level apical to that source. Clinical observations indicate that, once the biologic attachment is invaded around the implant, the gingival reactions are similar to those found around natural teeth, whether the tissue is of the thick flat or thin scalloped type.