A Plaque Glycolysis and Regrowth Method (PGRM) has been used to evaluate the in vivo antimicrobial activity of a new stabilized stannous fluoride dentifrice in comparison to a control dentifrice (Regular Crest, containing NaF) and a second commercial dentifrice containing SnF2. In the method, plaque collected from subjects prior to toothbrushing served as control for subsequent plaque samples collected following toothbrushing with assigned formulations. Inhibition of plaque metabolic activity was determined by the comparative acidogenicity of normalized plaque samples as contrasted with control plaques incubated similarly. Results from a sixteen-person cross-over study demonstrated that the improved stabilized stannous fluoride dentifrice significantly reduced plaque metabolism of sucrose in comparison to both placebo and commercial SnF2 dentifrice formulations following a single toothbrushing with 2.5 grams of dentifrice for over 90 minutes following treatment. These results support the strong antimicrobial activity of the stabilized stannous fluoride dentifrice, currently marketed as Crest Gum Care, in inhibiting plaque metabolism/acid production following in vivo toothbrushing.