The objectives of our study were to investigate the effects of water pretreatment by mean of coagulation, or MiEX® resin adsorption, on the removal of natural organic matter and on the fouling of membranes during the ultrafiltration process. In all cases water pretreatment resulted in an increase of permeate quality and a decrease of membrane fouling. However, the results indicated that treatment with MiEX® resin is much more effective than coagulation in organic substances removal. This was especially true for its lowmolecular fractions, which are responsible for membrane fouling.