A total of 108 adult male and female subjects completed a six-month, double-blind clinical study designed to compare the effect of a dentifrice containing 0.3% triclosan and 2.0% of a copolymer of methoxyethylene and maleic acid (Gantrez copolymer) in a 0.243% sodium fluoride/silica base to a 0.243% sodium fluoride/silica placebo dentifrice on supragingival plaque formation and gingivitis. Subjects were stratified into two balanced groups by their baseline plaque and gingivitis scores. They received an oral prophylaxis and were assigned to use either the triclosan/copolymer dentifrice or the placebo dentifrice for the next six months. After six months, the dentifrice containing triclosan/copolymer provided a 24.93% statistically significant (99% level of confidence) reduction in supragingival plaque, and a 19.72% statistically significant (99% level of confidence) reduction in gingivitis compared to the placebo dentifrice. Twice daily use of a dentifrice containing 0.3% triclosan, 2.0% of a copolymer, and 0.243% sodium fluoride in a silica base, over a six-month period, reduces supragingival plaque formation and gingivitis to a significant degree compared to a sodium fluoride/silica base placebo dentifrice.