The eight papers in this Special Issue of Functional Plant Biology span some of the highlights of the 4th International Congress on Crassulacean Acid Metabolism (CAM-2004), held at the Granlibakken Resort and Conference Center, Tahoe City, California, USA, 29 July–2 August 2004. International meetings of this small but dedicated cadre of globally dispersed CAM researchers have been infrequent until 2001 when the International Society of Crassulacean Acid Metabolism (ISCAM) (http://www.ag.unr.edu/cam/about.htm; validated 13 May 2005) was formally established. At the 3rd International CAM meeting held in 2001 in North Queensland, it was decided to make the International CAM Congress a more regular event, being held every third year in conjunction with the International Congress on Photosynthesis. A 5th International Congress on Crassulacean Acid metabolism (CAM-2007) is being planned for July 2007 in Cambridge, UK before the International Congress on Photosynthesis in Glasgow, UK. Previous meetings held in Riverside, CA (USA) in 1982 and in PanamaCity, Panama in 1993 each resulted inmonographs by Ting and Gibbs (1982) and Winter and Smith (1996). The CAM-2001 meeting resulted in the publication of a Special Issue of Functional Plant Biology. Following its success, we have been granted the opportunity to publish the results of the CAM-2004 proceedings in this Special Issue of Functional Plant Biology. I summarise below the highlights of the talks presented at the CAM-2004 meeting under four broad categories: economic importance; carbon acquisition, ecophysiology and evolution; circadian and environmental regulation; and intracellular transport processes. Crassulacean acid metabolism (CAM), a continuum of water saving photosynthetic carbonfixationmodes exhibiting