A chemical is classified as mutagenic in the Salmonella assay if it was evaluated as either “mutagenic” or “weakly mutagenic” by Zeiger (Gold and Zeiger, eds., Handbook of Carcinogenic Potency and Genotoxicity Databases, CRC Press, 1997, pp. 687-729; Zeiger, pers. comm.) or as “positive” by the Gene-Tox Program (Kier et al., Mutat. Res. 168: 69-240, 1986; Auletta, pers. comm.). Other chemicals evaluated for mutagenicity by these two sources are reported as non-mutagens. Of the 1547 chemicals in the CPDB, 860 have evaluations of mutagenicity in Salmonella from these sources.