The purpose of the present study was to clarify the potentiality of acidic fluoride solution in treating peri-implantitis. We examined bactericidal activity of fluoride solution against periodontal pathogens; and evaluated the effects of fluoride on titanium, and the effects on cell proliferation and differentiation of rat bone marrow cells on the fluoride-treated titanium. Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis were used to determine minimal inhibitory concentration (MIC) and shorttime exposure. The cells were seeded on the titanium surface with or without fluoride treatment. Then, cellular proliferation, differentiation and mineral deposition were analyzed. The MIC values for A. actinomycetemcomitans and P. gingivalis were 225 and 900 ppm F(-), respectively. In short-time exposure test, both bacterial strains exhibited a significant decrease in a concentrationdependent manner. Cell proliferation and mineral deposition were significantly increased on the fluoride-treated surface. Within the limitation of this study, acidic sodium fluoride solution has the potentiality in treating peri-implantitis.