Two strains, 199T and 176, of Gram-negative, anaerobic, rod-shaped, non-spore-forming bacteria were isolated during studies of microbiota in human faeces using polyamine-deficient medium. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the isolated strains belonged to the genus Bacteroides. The G+C content (42.4-43.0 mol%) and major fatty acid composition (anteiso-C15:0, 31.8-36.2 %) supported the affiliation of the two strains to the genus Bacteroides. 16S rRNA gene sequence similarities with their closest neighbours, Bacteroides thetaiotaomicron and Bacteroides ovatus, ranged from 94.6 to 96.5 %. DNA-DNA hybridization and phenotypic analysis showed that the two strains belonged to the same species (DNA-DNA relatedness of 89 %) and were distinct from their close relatives, B. thetaiotaomicron and B. ovatus (<23 % DNA-DNA relatedness). On the basis of these data, a novel species of the genus Bacteroides, Bacteroides finegoldii sp. nov., is proposed, comprising the designated type strain 199T (=JCM 13345T=DSM 17565T) and strain 176 (=JCM 13346).