text: The causal agents of destructive periodontal disease are several gram-negative bacteria. The mere presence, however, in the dental biofilm does not guarantee onset of the disease. The immunological and inflammatory host response as well as connective tissue and bone metabolism are strongly influenced by genetic, acquired and behavioural risk factors. Among the last, tobacco consumption holds a primary position. Prevalence, extent and severity of periodontitis as well as tooth loss and edentulism are influenced by tobacco consumption in a dose-dependent manner. About 50% of periodontal disease in young adults is attributable to cigarette smoking. Postoperative results in periodontally diseased smokers are considerably poorer than those achieved in non-smokers. As a consequence smoking cessation has to be in corporated in traditional treatment concepts for inflammatory periodontal disease.