Oregano and thyme, ground and sterilized with ethylene oxide, were added to culture broths YES (yeast extract sucrose) so that the final concentrations of the herbs were 0, 0.25, 0.5, 1, 2, and 4%. The broths were inoculated with a spore suspension of Aspergillus parasiticus and Aspergillus flavus and incubated at 25°C for 4, 7, 10, 14, and 21 d. Then, the growth of the cultures as mycelium dry weight and the production of aflatoxins (B₁ and G₁) by fluorimetry, after separation by thin layer chromatography (TLC), were determined. Although oregano and thyme stimulate the growth of both strains of molds, at the same time they act as antiaflatoxigenics.