Staphylococcus xylosus is a ubiquitous bacterium frequently isolated from mammalian skin and occurring naturally on meat and dairy products. A physical and genetic map of the S. xylosus C2a chromosome was constructed by pulsed-field gel electrophoresis analysis after digestion with AscI, ApaI, I-CeuI, SfiI and SmaI enzymes and hybridization analysis. The chromosome size was estimated to be 2868+/-10 kb. Thirty-three genetic markers were mapped. The probable origin of replication (oriC) was positioned. Six rrn loci were located, and their orientation was determined. The chromosomes of six additional S. xylosus strains were also analysed by I-CeuI digestion, and an intraspecies diversity of the chromosome size and the number of rrn operons was shown.