Strains originally identified phenotypically as members of the species Yersinia pseudotuberculosis were subjected to a more detailed classification employing 16S rRNA gene sequence analysis, DNA-DNA hybridization, determination of the DNA base composition and phenotypic characterization. The quinone system, consisting of the predominant compound ubiquinone Q-8 and minor amounts of menaquinone MK-8, the major components of the polar lipid profile, as well as the polyamine pattern, with putrescine as the major compound, supported the assignment of the strains to the genus Yersinia. Based on DNA-DNA relatedness, a specific 16S rRNA gene sequence type, absence of melibiose fermentation and a polar lipid profile lacking phosphatidylmonomethylethanolamine and two aminolipids, the strains were identified as members of a novel species for which the name Yersinia similis sp. nov. is proposed. The type strain of Yersinia similis sp. nov. is strain Y228T (=CCUG 52882T=LMG 23763T).