Sequence-tagged sites (STSs) are key elements in efforts to construct and integrate the various physical maps of a genome. We report the development of 21 STSs assigned to cosmids mapped to specific locations on human chromosome 19 by fluorescence in situ hybridization (FISH). At least one STS has been assigned to each band. The PCR primers generate a single product from genomic DNA. Each product is a single copy probe for Southern blots of human genomic DNA. YACs have been identified with 18 of these STSs.