Two strains of a previously undescribed Eubacterium-like bacterium were isolated from human faeces. The strains are Gram-variable, obligately anaerobic, catalase negative, asporogenous rod-shaped cells which produced acetate, butyrate and lactate as the end products of glucose metabolism. The two isolates displayed 99.9% 16S rRNA gene sequence similarity to each other and treeing analysis demonstrated the faecal isolates are far removed from Eubacterium sensu stricto and that they represent a new subline within the Clostridium coccoides group of organisms. Based on phenotypic and phylogenetic criteria, it is proposed that the two strains from faeces be classified as a new genus and species, Anaerostipes caccae. The type strain of Anaerostipes caccae is NCIMB 13811T (= DSM 14662T).