The commercial hydrotreating catalysts are usually composed of a sulfide active phase supported on alumina. It has been known for more than 15 years that other supports might lead to enhanced catalytic properties. The present article summarizes the progress which have been made in this area, often related to new methods of preparation of supports, active phases deposition or activation procedures. The properties of active phases supported on oxides, pure or mixed, basic and acidic supports, zeolites, mesoporous materials, carbon and clays are examined. (C) 2003 Elsevier B.V. All rights reserved.