Sixteen fungi and fife bacteria were isolated from soya beans and their species were determined. The microorganisms were cultivated on soya flour agar plates sterilized by heat. After addition of an enriched lipoxigenase preparation the growth was followed. The fungi but not the bacteria were all, to a varying degree, inhibited. Obviously the lipoxygenase peroxidizes the substrates occuring in the soya flour to compounds that inhibit the growth of the fungi.