Microbiological contamination of polymeric membranes in the process of their exploitation is an essential problem of membrane technology. It results in the increase of manufacturing, costs, destruction of membranes, operating life reduction and secondary contamination of water by the metabolism products of microorganisms. For the purpose of reduction of membrane biofouling and biodegradation investigation of adsorption of the guanidine containing oligomers on the surface of PET track membranes was conducted and their influence on the selectivity and antibacterial properties of the membranes was investigated. It was established that modified membranes have substantially higher resistance to biofouling.