Butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) were applied to six strains of toxigenic and six strains of non‐toxigenic Aspergillus flavus in a method similar to antibiotic susceptibility testing. The cultures were examined for growth inhibition, spore formation, pigmentation, and aflatoxin production. BHA (0.005–0.020 g per plate) had an inhibitory effect on growth and toxigenesis of the test organisms, while BHT (0.005–0.020 g per plate) had no visible inhibitory effects. Sporulation of the cultures had no direct relationship with toxigenesis in the presence of BHA. However, pigmentation of the mycelium is directly related to the intensity of fluorescence of the culture under UV. Heating of BHA did not reduce the inhibitory effect of the compound on A. f