We present a radiation hybrid (RH) map of human Chromosome (Chr) X, using 50 markers on 72 radiation hybrids. The markers, obtained from the consensus map, form a grid spanning the entire chromosome. To check the RH map, the marker order was determined by analysis of presence or absence of retained human DNA fragments in the RHs; the comparison with the consensus showed a similar order. Any STSs, microsatellites, genes, and clones can be positioned and ordered relative to the marker grid. This approach integrates genetic, physical, and large-scale clone mapping and is used to link YAC contigs containing data from various experimental sources.