Aim of the study: to characterise a rat model of periodontitis for use in functional studies by analysis of alveolar bone loss in rats with experimentally-induced periodontitis. Methods: Periodontal inflammation was induced by a single injection of 10 mg liposaccharide (LPS) (Salmonella typhimurium) in 1ml saline into rat mandibular gingiva at the buccomesial aspect of the second molar. Animals were killed after 7 days, mandibles dissected and sectioned for histological and immunocytochemical analysis. Results: There was an 80% increase in the alveolar bone loss, measured as the distance between alveolar crest and the cemento-enamel junction, in LPS-injected animals compared to controls (468±230µm control, 830±270µm LPS, pConclusion: Intragingival injection of LPS in the rat provides an easily induced reproducible experimental model of periodontal inflammation that reiterates features of human disease. Schlagwörter: bone resorption, inflammation, lipopolysaccharide, osteoclast activation, periodontitis