cMap, a www comparative genetic map graphical utility, has a search capability and provides comparison of two genetic maps within or between species with dynamic links to data resources and text lists of the shared loci, running in a relational database environment. Currently, maps from three species (maize Zea mays L., rice Oryza sativa L., and sorghum Sorghum bicolor L.), representing over 13,800 distinct loci, are available for comparison at http://www.agron.missouri.edu/cMapDB/cMap.html.