The objective of this double-blind clinical study was to investigate the effectiveness of a dentifrice containing triclosan and a copolymer, Colgate Total Toothpaste, for controlling breath odor twelve hours after brushing the teeth compared to a placebo dentifrice which did not contain triclosan or a copolymer. Breath odor was evaluated by a panel of four expert judges using a nine-point hedonic scale. Following a baseline evaluation of breath odor, prospective study subjects who presented scores above the threshold value for unpleasant breath odor were stratified by score, and randomized into two treatment groups. Subjects were provided with a soft-bristled toothbrush, and brushed their teeth thoroughly in their regular and customary manner with their assigned dentifrice. Subjects refrained from dental hygiene, breath mints, or mouth rinses for the next twelve hours, after which they were once again evaluated for breath odor. Sixty-three (63) adult male and female subjects from the Mississauga, Ontario, Canada area participated in the study. At twelve hours after brushing their teeth, subjects in both dentifrice treatment groups presented mean breath odor scores which were statistically significantly lower than the mean scores observed at baseline. However, the difference between the mean twelve-hour breath odor scores differed significantly between the two dentifrices. The mean twelve-hour breath odor score for the Colgate Total Toothpaste group was 4.77, which is within the range of values corresponding to pleasant breath odor; the mean twelve-hour breath odor score for the placebo group was 6.05, which is above the value corresponding to unpleasant breath odor. Thus, the results of this double-blind clinical study support the conclusion that Colgate Total Toothpaste provides effective control of breath odor at twelve hours after brushing the teeth.