We have constructed a high-resolution cytogenetic map of human chromosome 5 with 206 new cosmid clones by direct R-banding fluorescence in situ hybridization. The fluorescent signals of 206 clones were evenly distributed throughout chromosome 5, although they were sublocalized preferentially to R-positive bands. This high-resolution cytogenetic map with an average distance of nearly 1 Mb will serve as important resource for construction of a genetic linkage map, which is essential for positional cloning of responsible genes. Moreover, these mapping data provide many useful landmarks for the construction of contig maps of chromosome 5, as required in the Human Genome Project.