The previous study indicated that the extracts of three form of Hom Nil rice (Oryza sativa) and black glutinous rice (Oryza sativa var. glutinosa); raw, cooked and fermented were not mutagenic. But after nitrite treatment, these rice extracts exhibited their mutagenicity. In this study, extracts of raw, cooked and fermented Hom Nil rice and black glutinous rice was explored using Ames test on Salmonella typhimurium TA98 and TA100. Rice extracts was added to nitrite-treated chicken extract at levels of 0.8, 1.2 and 1.6 mg/plate. Addition of raw and cooked rice extracts enhanced the mutagenicity of nitrite-treated chicken extracts. However, extracts of both types of fermented rice inhibited mutagenic activity of mutagen occurred during nitrite-treated chicken extracts according to fermentation might increase some active compounds or change some certain compounds that resulting in reduced the mutagenicity of nitrite-treated chicken extracts. Nevertheless, the actual mutagenicity index (MI) of the mixture of sodium nitrite treated chicken extract in the presence of each rice extract was rather less than that of the expected MI that obtained from summation of individual MI obtained from sodium nitrite treated chicken extract and each sodium nitrite treated rice extract on both strains. Only the mixture of chicken extract and cooked black glutinous rice extract at the amount 0.8 mg/plate yielded actual MI greater than expected from summation of individual MI on S. typhimurium TA98. However, the cooked black glutinous rice extract showed the negligible effect. The effects of these rice extracts might be due to the presence of some antimutagen components that might reduce nitrosation reaction, and/or scavenge mutagen and/or free radicals that occur during mutagenesis, and/or changing some bacterial properties. The results from this study suggest that consumers should avoid the consumption of the black glutinous rice and Hom Nil rice with nitrite-containing food.