The antibacterial activity of 4 triclosan-containing toothpastes was compared to a conventional fluoride dentifrice and triclosan and sodium lauryl sulphate (SLS), both singly and in combination. A panel of 17 bacteria was tested by an agar dilution method. At concentrations typical of those found in toothpastes, triclosan and SLS displayed approximately equal antibacterial activity. A paste containing triclosan and zinc citrate appeared more active than the other triclosan pastes which, in general, showed marginal superiority over the conventional paste. SLS, although included in dentifrice formulations for its detergent properties, may significantly contribute to the antibacterial profile of a product. The need for appropriate controls when evaluating experimental toothpastes is emphasized.