Addition of migillin to the nutrient medium at early stages of the fungus development induced at one hand inhibition of the fungus growth during the first 24-48 hours and stimulation of the biomass accumulation during the following hours of the development and on the other hand it induced inactivation of migillin added and inhibition of production of the "own" antibiotic. The migillin effect was accompanied by a delay in liberation of the substance with adsorption at 260nm from the mycelium.