A number of possible bases for a biological assay for the aflatoxins were examined, of these two were selected for further study. An inhibition assay using Bacillus megaterium was developed in combination with thin layer chromatographic analysis. This method was capable of detecting 0.1 μg of aflatoxin B1 and of differentiating between various mycotoxins. An induction assay using a lysogenic strain of Bacillus megaterium was also developed. This assay has a sensitivity of 2-4 μg/ml aflatoxin B1 and is claimed to be more specific than the inhibition assay. A number of other mycotoxins were examined to test the versatility and specificity of the assays. The inhibition assay was able to detect and differentiate between most of the toxins. The induction assay detected only those mycotoxins reported or suspected to be carcinogenic.