Many compounds could be added to toothpaste to assist plaque inhibition, but ionic interactions can cause formulation difficulties. Moreover, the actual chemical action of a plaque inhibitory agent added to a toothpaste is difficult to assess when the product is used in the conventional manner, i.e., in addition to toothbrushing. The non-ionic antimicrobial triclosan has been incorporated in toothpastes and shown to have variable plaque inhibitory activity both alone and in conjunction with certain polymers or metal ions. Little is known of the efficacy of triclosan toothpastes compared to conventional fluoride toothpastes. The aim of this study was to compare a commercially available toothpaste containing 0.3% triclosan/co-polymer with a sodium fluoride toothpaste for chemical plaque inhibitory effects over a 4-day period. The study was designed to stratify the relative efficacy plaque inhibitory action of the products, comparisons were made with a positive control, chlorhexidine rinse and a negative control, saline. The study design was a randomised single blind crossover design balanced for first-order carryover. A total of 18 healthy, dentate volunteers participated in the study. On day 1 of each period the volunteers suspended toothcleaning and rinsed 2 x daily with the allocated mouthrinse or toothpaste slurry. On day 5, the plaque on the teeth was disclosed and scored by index and area. Increasing plaque scores were in the order chlorhexidine, triclosan toothpaste, fluoride toothpaste, and saline. Chlorhexidine was significantly more effective than all the other agents tested, and both toothpaste preparations were significantly better than the saline rinse. There was no significant difference between the two toothpaste rinses. Consistent with other studies the triclosan toothpaste offers only moderate plaque inhibitory properties when compared to a conventional toothpaste.