The mutagenicity of aqueous extracts of four Nigerian food additives namely Xylopia aethiopica (Xa), Monodora species (Ms); fermented Litrillus lanatus-ogiri (Og) and fermented Parikia africans (African locust bean)-Iru (Ir) alone and in combination with different concentrations of aflatoxin B1 (0.05 microgram-0.25 micrograms) in the presence and absence of fecalase was studied using the Ames' salmonella mutagenicity assay system. Preliminary screening tests show the tester strain TA98 to be the most sensitive of the four tester strains (TA97, TA98, TA100, TA102) screened. The most mutagenic of the doses of the extracts are 3mg each of Xa and Ms per plate and 5mg each of Og and Ir per plate. A combination of these doses with different concentrations of aflatoxin B1 resulted in an enhanced mutagenicity of aflatoxin B1. The increases could not be accounted for by additive mutagenicity of the extracts and aflatoxin B1. Fecalase further increased the effects resulting from these combinations with the exception of Xa which showed a decrease in mutagenic induction. The increase may be indicative of the presence of some mutagenic glycosides in the extracts.