Smoking is the most important environmental risk factor for the initiation and progression of periodontitis. However, its effect on periodontopathic Porphyromonas gingiavalis with respect to changes in physicochemical characteristics and prevalence of the pathogen in periodontitis patients remain to be elucidated. The present study was performed to examine the effect of cigarette smoking on the growth, protein profile, and prevalence of P. gingivalis genotypes in smoker and non-smoker periodontitis patients. The growth of P. gingivalis strains 2561 and 9-14K-1 in cigarette puffdissolved culture medium (CM) for 24 and 48 h was inhibited approximately 40% as compared to their growth in non-CM, but the growth of strains A7A1-28 and W50 was inhibited in CM by approximately 15%, revealing that they were relatively resistant to cigarette puff. In contrast, the growth of P. gingivalis HNA-99 was enhanced in CM by 11% after the 24-h incubation. However, its growth after the 48-h incubation decreased by 11% in CM. SDS-polyacrylamide gel electrophoresis and immunoblot analyses demonstrated that the expression of fimbriae in P. gingivalis strains 2561 and 9-14K-1, which were sensitive to cigarette puff, was reduced. On the other hand, the expression of fimbriae was rather increased in the cigarette puff-resistant strains A7A1-28 and W50. Decrease in autoagglutination of P. gingivalis 2561 grown in CM supported the fact that fimbrial expression in the cigarette puff-sensitive strain 2561 had been diminished. Genotypes of P. gingivalis in the subgingival plaque from 22 smoker and 32 non-smoker periodontitis patients was examined by 16S rRNA fimA gene-directed PCR. The prevalence of P. gingivalis was higher in the smokers (95.5%) than in the non-smokers (81.3%). Among the 5 fimA genotypes of P. gingivalis, genotype V, to which the cigarette puff-resistant strain HNA-99 belongs, was most prevalent in the non-smokers (57.4%). Although genotype V was found in 59.1% of the smokers, its prevalence in the smokers was second to that of genotype II. Genotype II, of which A7A1-28 is a representative, was observed to be predominant and seemed to be more closely related to smoking since its occurrence in the smokers was 63.6%, but only 21.9% in the non-smokers. The overall results suggest that cigarette smoking may directly affect physicochemical characteristics of P. gingivalis including the expression of fimbriae, which may play an important role in the resistance of the bacterium to cigarette puff. Therefore, P. gingivalis strains that can express fimbriae under cigarette puff-conditions may be favored to survive the conditions.