The aims of the study were (1) to compare the anticaries efficacy of a silica abrasive dentifrice containing 0.24% NaF and 0.3% triclosan/2.0% copolymer with a similar dentifrice without the triclosan/copolymer and (2) to study any disturbance of the oral mucosa associated with the test formulation. A double-blind, random, unsupervised, 30-month longitudinal clinical trial was conducted on 3,462 children who were initially 11-13 years of age. Two trained and calibrated dentists each examined approximately half the children. Examinations were undertaken at baseline, 15 months and 30 months. No significant differences were found between the DFS or DFT mean increments for the two dentifrice groups after 15 or 30 months. At 30 months the 90% confidence interval for the ratio of the mean increments satisfied the ADA criteria for equivalence. It is concluded that a 0.24% NaF/silica abrasive dentifrice containing 0.3% triclosan/2.0% copolymer is equivalent in its anticaries efficacy to a similar dentifrice without the addition of triclosan/copolymer. No side effects attributable to the test or control dentifrices were observed at any time during the study.