ln order to investigate the mutagenic activity of Meju, an important component of the Korean diet, both chemical techniques and the Ames test were used. To determine if antimutagenic activity is present in Meju and other soybean based foods, the Ames Test was done in the presence of aflatoxin B₁, benzo(a)pyrene, and other mutagens. Although aflatoxin contamination was found in 6 of 43 samples of Meju tested, the amounts were less than 1 ppb in all but one. Meju had a protective effect against mutations produced by both aflatoxins and benzo(a)pyrene, both of which act via an epoxide, but not against other mutagens tested.