In previous studies with aflatoxin-contaminated corn an uncharacteristic response for AFB1in the Salmonella/microsomal mutagenicity assay (Ames test) was observed and the presence of anti-aflatoxin factors in the corn was suggested. In the current study, corn was extracted and fractionated using thin layer chromatography (TLC) using different developing solvent systems and the Ames test was used to monitor for anti-mutagenic activity in the corn fractions. Both Salmonella tester strains TA98 and TA100 with metabolic activation (S9) were used. Several corn fractions, at different stages in the isolation and purification process, showed anti-mutagenic dose-responses when exposed to pure AFB1. Corn extracts were non-toxic to the tester strains and TLC fractions that showed the best anti-mutagenic dose-responses were selected for further partial characterization analyses. © 2001 Taylor & Francis Group, LLC.