The purpose of this study was to evaluate the antimicrobial activity of Crassirhzimae rhizoma and its possible use as an oral antiseptics for prevention of periodontitis. Its antibacterial activity against periodontopathic microorganisms including Actinobacillus actiomycetemcomitans, Capnocytophaga ochracea, Streptococcus mutans, Porphyromonas gingivalis, Prevotella intermedia, Actinomyces viscosus, Fusobacterium nucleatum was evaluated via modified stab culture method. The cytotoxicity against gingival fibroblasts and rat osteoblasts was investigated via [³H]thymidine incorporation and cellular activity was investigated via MTT assay. Chlorhexidine was used as control group. Crassirhizomae rhizoma was prepared at concentrations of 0.2, 0.15, 0.1, 0.05%. Chlorhexidine was also prepared at the same concentration. Crassirhizomae rhizoma showed lower antimicrobial antivity against these microorganism than chlorhexidine, but this difference was not significant. And, Crassirhzomae rhizoma showed more cellular activity and less cytotoxicity than chlorhexidine on human gingival fibrablast and rat osteoblast. This study suggests that Crassirhzomae rhizoma might be a candidate for a safe oral antiseptic for the prevention and treatment of periodontal disease.