The seawater reverse osmosis system requires extensive pre-treatment in order to ensure reliable performance. The conventional pretreatment system involves dosing of chemicals, which requires frequent monitoring of raw water quality, and also involves adjusting the dosage. Besides being cumbersome, there is a lot of time lag involved in carrying out these measures. This calls for pre-treatment systems based on physicochemical mechanisms. During the last few years, Ultrafiltration (UF) has emerged as a leading unit operation in order to render raw seawater compatible with reverse osmosis operations. In this context, the Desalination Division of BARC has already installed an operational UF pre-treatment system. In this paper, we examine the role of UF in the overall operations of the seawater reverse osmosis system. Copyright © 2006 Inderscience Enterprises Ltd.