Periodontal disease is a significant cause of alveolar bone resorption resulting ultimately in the loss of teeth. Inflammation of the periodontal tissues is initiated by bacteria of the oral micro-flora. Invading micro-organisms stimulate both protective and destructive inflammatory-immune responses involving cytokine release syndrome, chemokines, arachidonic acid metabolites, reactive oxygen and nitrogen intermediates, and matrix melloproteinases. The local infection may affect general health in two ways. First, transient bacteremia from the oral focus may result in metastatic infection in remote organs of susceptible hosts, such as bacterial endocarditis in patients with congenital or acquired heart diseases. Second, lipopolysaccharide and inflammatory mediators are not only involved in local tissue destruction but have the potential to modulate the course of cardiovascular, chronic obstructive lung and autoimmune diseases, diabetes mellitus and preterm birth. Epidemiologic observations, awaiting further verification by controlled prospective trials, underline the impact of oral health on general well-doing.