A double-blind cross-over clinical study was performed on eight volunteers to determine the plaque-inhibiting effect of different triclosan- and sodium lauryl sulfate (SLS)-containing mouthrinses. An attempt was also made to locate the binding site(s) of triclosan in the oral cavity. After the volunteers rinsed for four days with solutions of various concentrations of triclosan and/or SLS, plaque deposits were scored according to the Silness and Löe Plaque Index. The study showed that 0.15% and 0.3% concentrations of triclosan yielded a comparable plaque-inhibiting effect in vivo. Furthermore, the 0.1% triclosan with 1.5% SLS exhibited a higher (though not significant) effect than 0.1% triclosan with 0.75% SLS. The mouthrinse containing 0.05% triclosan and 0.25% SLS was as effective as the two mentioned mouthrinses containing 0.1% triclosan. Collectively, the results indicate that triclosan alone has an antiplaque effect, independent of the effect of SLS. Furthermore, the results suggest that the SLS monomers may play a role as carriers of triclosan and that the teeth are not the only binding site of triclosan, since topical application of 0.3% triclosan failed to produce a clinically discernible effect.