The purpose of this paper is to focus on functional characteristics of leukocyte adhesion molecules, on their localization and specific ligands. In fact, leukocyte chemotaxis and adhesion to endothelium is an essential step in promoting adequate immune response to bacterial infections. Since periodontal health is highly dependent on neutrophil function against the microbial dental plaque, defects in chemotaxis and adhesion of leukocytes to endothelium often result in severe, early onset periodontitis. Furthermore, oral lesions may be the only clinical manifestation of neutrophil impairment.