The nucleotide sequences of the 165 rRNA gene (rDNA) in 38 taxa of the genus Staphylococcus were compared phylogenetically. Based on phylogenetic tree analysis, staphylococcal Species Were divided into 12 Cluster groups. These cluster groups were in very good agreement with species groups determined by DNA-DNA reassociation studies. These genealogical classifications were consistent with the results of the production of coagulase or oxidase and with resistance to novobiocin. These suggest that the phylogenetic relationship of the genus Staphylococcus is accurately represented by the results obtained from the sequence analysis of 165 rDNA.