This document discusses the relationship between smoking and periodontal disease. It begins by introducing tobacco smoking as a detrimental habit and risk factor for systemic diseases. It then explores the constituents of tobacco smoke and the mechanisms by which smoking can increase toxicity and periodontal disease risk. Subsequent sections examine the effects of smoking on plaque, periodontal tissues, immunology/host response, and how smoking may impact periodontal therapy and systemic health. The document concludes by emphasizing the long-term chronic negative effects of smoking on the periodontium.