['The purpose of the present study was to determine the effect of smoking cessation on gingival blood flow (GBF) and gingival crevicular fluid (GCF).', 'Sixteen male smokers (aged 22-39 (25.3+/-4.0) years), with no clinical signs of periodontal and systemic diseases, were recruited. The experiment was performed before (baseline) and at 1, 3 and 5 days, and at 1, 2, 4 and 8 weeks after smoking cessation. The status of smoking and smoking cessation was verified by exhaled carbon monoxide (CO) concentration, and by serum nicotine and cotinine concentrations. A laser Doppler flowmeter was used to record relative blood flow continuously, on three gingival sites of the left maxillary central incisor (mid-labial aspect of the gingival margin and bilateral interdental papillae). The GCF was collected at the mesio- and disto-labial aspects of the left maxillary central incisor and the volume was calculated by the Periotron 6000(R) system. The same measurements except for the GBF were performed on 11 non-smoking controls (four females and seven males), aged 23-27 (24.4+/-1.2) years.', 'Eleven of 16 smokers successfully completed smoking cessation for 8 weeks. At 1 day after smoking cessation, there was a significantly lower CO concentration than at baseline (p<0.01). Also, nicotine and cotinine concentrations markedly decreased at the second measurement. The GBF rate of smokers was significantly higher at 3 days after smoking cessation compared to the baseline (p<0.01). While the GCF volume was significantly increased at 5 days after smoking cessation compared to the baseline (p<0.01), it was significantly lower than that of non-smokers until 2 weeks after smoking cessation (p<0.01).'] Does smoking cessation increase gingival blood flow and gingival crevicular fluid?