Eubacterium exiguum sp. nov. is the name proposed for organisms formerly described as Eubacterium group S strains and similar bacteria isolated from various types of oral lesions. This new species was established on the basis of the results of DNA-DNA hybridization experiments and DNA base composition determinations (G+C contents, 60 to 64 mol%). The results of an API ZYM analysis, Western blotting (immunoblotting) reactions, and phenotypic tests are also given. The type strain of E. exiguum is strain S-7.