The aim of the present clinical trial was to study the effect on existing plaque and gingivitis of an oral hygiene regimen which utilized a dentifrice which contained triclosan. 120 subjects were recruited for the trial. They were examined for plaque and gingivitis using the criteria of (i) the Turesky modification of the Quigley & Hein plaque index and (ii) the Löe & Silness gingival index. Plaque and gingivitis were assessed in all parts of the dentition and at 6 location points around each tooth. Following a baseline examination, the subjects were stratified in 2 balanced groups based on age, plaque and gingivitis scores. The subjects were randomly assigned to the following treatment: 1 test group used a dentifrice containing triclosan/copolymer/fluoride and 1 control group used a traditional fluoride containing dentifrice. The participants were given the assigned dentifrice and a soft-bristled toothbrush for home use. They were instructed to brush their teeth in the morning and in the evening for one minute each time. They were reexamined 6 weeks, 3 and 6 months after the baseline examination. The findings from the re-examinations revealed that an oral hygiene regimen which utilized a dentifrice which contained triclosan/copolymer significantly reduced pre-existing plaque and gingivitis above what was accomplished by a traditional fluoride containing dentifrice. The improvement of the gingival conditions occurred in all parts of the dentition and at all tooth surfaces and units. In addition, the present data support the hypothesis that triclosan may induce alterations in the quality of existing plaque.