Integrated membrane systems have been recently proposed as suitable alternatives to overcome existing limitations in traditional seawater reverse osmosis desalination plants. By this approach, submerged hollow fiber ultrafiltration have been chosen as pretreatment because of the lower energetic consumption and the great significance for reducing particles deposition on the membrane. This work focuses on the study of the influence of a set of operating conditions and the fouling dynamics when operating submerged ultrafiltration under subcritical flux conditions for relatively long-time. According with results, submerged hollow fiber ultrafiltration can be considered as a feasible pretreatment in reducing natural organic matter from seawater, provided that the opportune operating conditions were well identified and optimized. (C) 2010 Elsevier BM. All rights reserved.