Tobacco, particularly tobacco smoking, has a substantial influence on periodontal health and disease. It is associated with an increased disease rate in terms of periodontal bone loss, periodontal attachment loss, as well as periodontal pocket formation. In addition, it exerts a masking effect on gingival symptoms of inflammation. Risk assessment based on an increasing body of investigations over the past few years suggests that the tobacco attributable risk is considerable, estimated odds ratios being of the order 2.5 to 6.0 or even greater. Although the mechanisms by which tobacco exerts its influence are obscure, information available to date does not support the view that its action simply relates to other environmental factors such as the dental plaque or some specific microflora. It seems more likely that it primarily has a systemic influence affecting host response or susceptibility. The chief novelty of the present report is that current data suggest that, although the overall disease prevalence is decreasing, the proportion of periodontal disease attributed to tobacco is stable or even increasing. This seems to be analogous to what has been observed for other smoking-associated chronic diseases. This, in turn, indicates that periodontal disease behaves like several other chronic diseases and, further, that tobacco should be considered a major risk factor for chronic periodontal disease.