The present investigation was performed to examine if triclosan and a copolymer, incorporated in a dentifrice and used by periodontitis-susceptible subjects could influence clinical symptoms characteristic of recurrent periodontitis. 60 subjects, 34 to 67 years of age, were recruited for the study. They were randomly selected from a group of patients previously treated for advanced periodontal disease. This treatment had included oral hygiene instruction, subgingival debridement, but no surgical therapy. The patients had, during a 3-5 year period following active therapy, been enrolled in a maintenance care program but had, at various intervals, exhibited signs of recurrent periodontitis. The patients were stratified into 2 balanced groups with respect to mean probing pocket depth. The test group, included 30 individuals who used a dentifrice containing triclosan/copolymer/fluoride, i.e. 0.3% triclosan, 2% copolymer and 1100 ppm F from 0.243% sodium fluoride (Colgate Total). The control group also included 30 subjects who used a dentifrice identical to the one used in the test group but without the triclosan/copolymer content. Following the baseline examination, including clinical and radiographical assessments, all volunteers received detailed information on how to brush their teeth in a proper way. This information was repeated on an individual need basis during the course of the subsequent 36 months. No professional subgingival therapy was delivered between the baseline and the 36-month examinations, but the subjects were recalled every 3 months. Re-examinations were performed after 6, 12, 24, and 36 months of the trial. A 2nd set of radiographs was obtained at the final examination, i.e., at 36 months. The results demonstrated that in subjects susceptible to periodontal disease, meticulous, self-performed, supragingival plaque control maintained over a 3-year period failed to prevent recurrent periodontitis. In a similar group of subjects and plaque control program, however, the daily use of a triclosan-containing dentifrice reduced (i) the frequency of deep periodontal pockets, and (ii) the number of sites that exhibited additional probing attachment and bone loss.