There is a growing body of scientific evidence to support the concept that the use of tobacco products significantly contributes to the progression of periodontal disease or is detrimental to healing following periodontal therapy. Several studies have shown toxic effects of nicotine on peripheral circulation and the immune response. The purpose of the present study was to identify and compare the quantity of nicotine present on root planed and nonroot planed surfaces of teeth from smokers. Twenty-nine single-rooted teeth from 11 smokers were extracted, brushed clean, and the roots sectioned longitudinally. The respective halves were either left untreated (Group A) or thoroughly root planed (Group B). Pulpal tissue was removed and the individual root sections weighed. Each half was extracted for nicotine using a methylene chloride technique. Quantification was performed using high pressure liquid chromatography (HPLC) and the sections compared on a nicotine per root weight basis. Results showed a greater amount of nicotine present on non-root planed sections than on treated sections, although some treated specimens revealed small amounts of the substance. These findings suggest that nicotine is present on the root surface but is largely removed by thorough root planing. Its presence is not surprising in light of the recent finding that nicotine and cotinine, the major metabolite of nicotine, are found in gingival crevicular fluid. Recent studies have shown a particularly harmful effect of nicotine on fibroblasts. Its presence on root surfaces may, therefore, impair wound healing and alter the host response in periodontal disease. The use of tobacco products in conjunction with periodontal therapy may interfere with optimal healing and/or lead to further periodontal breakdown.