Two types of pretreatment systems are typically used to protect seawater reverse osmosis membranes from fouling: conventional granular media filtration and membrane filtration. While granular medial filtration is still a dominating seawater pretreatment technology, microfiltration and ultrafiltration membrane systems for seawater pretreatment have evolved rapidly over the past decade and may offer cost and performance benefits for the site specific conditions and challenges of a given seawater desalination project. This article presents a critical review of widely used conventional granular and membrane pretreatment technologies and addresses key factors, and issues which would need to be taken under consideration when selecting a seawater pretreatment system. (c) 2010 Elsevier B.V. All rights reserved.