The effect of adding 15% talc to either a standard periodontal disease-producing diet (Diet 2000) or a laboratory chow (Purina) was studied in the Syrian golden hamster. The additive was found to reduce the amount of periodontal disease with Diet 2000 and also change the characteristics of the plaque. The addition of talc to laboratory chow increased the severity of normally occurring periodontal disease, although not to the level of Diet 2000.