An in situ study was conducted to evaluate the effect of a dentifrice containing 1100 ppm F (NaF) and triclosan, an anti-plaque agent, on remineralization of artificially-formed caries lesions in thin sections of human enamel. The thin sections were placed in mandibular partial dentures of 15 subjects and covered with a steel mesh to provide an area for plaque accumulation. The subjects brushed their teeth and dentures three times daily for two-week periods in a cross-over design, after which the specimens were removed and analyzed by quantitative microradiography for changes in mineral content. Results showed that lesions treated with the triclosan-fluoride product were remineralized 18.0 +/- 23.4% compared with 19.0 +/- 32.3% from a 1100-ppm F (NaF) positive control. Use of a placebo dentifrice resulted in 71.9% demineralization. The findings showed that triclosan neither enhanced nor interfered with the promotion of remineralization by fluoride.