We assessed the potentiality of reducing concentration polarization and enhancing ultrafiltration of macromolecules via gas sparging (gas bubbles supplied to the UF system with the feed solution). Consideration was given to the problem of how the quantity of the gas sparged and the duration of the process affect the transport and separation properties of hollow-fibre UF modules. Ultrafiltration tests were carried out with model solutions containing macroparticles either organic (dye) or mineral (kaolin). Gas sparging was found to increase the permeability of the module by approximately 25%, but there was a slight deterioration of selectivity. The rate of gas flow seems to be of negligible importance.