The predominant reagents used in the mineral processing industry are reviewed and their mode of action briefly described. Inorganic, naturally derived organic and synthetic organic reagents, both old and new, all play a large part in successful processing particularly in froth flotation and in solid-liquid separation. The drive for new and improved reagents is both technical and environmental and reflects the ever evolving challenges of the industry. (C) 2004 Elsevier Ltd. All rights reserved.