Prevention mouthrinse was designed to serve as a vital supplement to normal oral hygiene procedures. To determine the antimicrobial potency of this mouthrinse, minimal inhibitory concentrations (MICs), bactericidal kinetics, and short-term exposure studies were conducted. A spectrum of oral microorganisms was employed in this investigation: Streptococcus sanguis, Streptococcus anginosus, Streptococcus mutans, Actinomyces viscosus, Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum, Eikenella corrodens, Porphyromonas gingivalis, Serratia marcescens and Candida albicans. Microorganisms were cultured in standard enriched media and under appropriate atmospheric conditions. Inhibition assays were conducted in tubes, with each mouthrinse dilution assayed in triplicate. MIC determinations revealed that all of the microorganisms studied were highly susceptible to Prevention mouthrinse, with MICs ranging from 16-fold to 128-fold dilutions. Bactericidal kinetics assays showed rapid killing of the test organisms in the presence of the mouthrinse. Brief (5-minute) exposure of S. mutans to 8-fold diluted mouthrinse resulted in a substantial delay in growth. Under the constraints of this type of study, Prevention mouthrinse exhibited potent antimicrobial activity against all of the microorganisms studied. We support the notion that Prevention mouthrinse may be a valuable supplement to normal oral hygiene procedures. A 6-month clinical trial assessing the in vivo efficacy of Prevention mouthrinse is currently being conducted.