ABSTRACT: Periodontitis is the result of complex interrelationships between infectious agents and host factors. Environmental, acquired, and genetic risk factors modify the expression of disease and may, therefore, affect the onset or progression of periodontitis. The study of the relationship between periodontal disease and smoking has received increased attention during the last few years. Tobacco smoking has wide spread systemic effects, many of which may provide mechanisms for the increased susceptibility to periodontitis and the poorer response to treatment. Tobacco smoking is a significant risk factor for periodontal disease.