The antibacterial efficacy of a mouthrinse(Denta Gargle) containing CPC(cetylpyridinium chloride), NaF and UDCA(ursodeoxycholic acid), on major periodontopathogens, was in vitro examined and compared with that of Listerine by a broth dilution method. The bacteria tested were Actinobacillus actinomycetemcomitans, Bacteroides forsythus, Fusobacterium nucleatum subsp. vincentii, Prevotella intermedia, Porphyromonas gingivalis and Treponema denticola. The growth of all the bacteria were completely inhibited by a 1-min exposure to the both mouthrinses. When diluted at 1:5 or more, all bacteria analyzed but P. intermedia were not inhibited by Listerine. In contrast, Denta Gargle showed highly increased maximum inhibitory dilutions(MID) against all periodontopathogens included in this study, with MIDs ranging from 5-fold(F. nucleatum) to 160-fold dilutions(P. intermedia). The MIDs against A. actinomycetemcomitans, B. forsythus, P. gingivalis and T. denticola. were 1:40, 1:80, 1:80 and 1:80, respectively.