Seven recently cultured bacterial isolates, although similar in their 16S rRNA gene sequences to Roseburia intestinalis L1-82(T) (DSM 14610(T)), were not sufficiently related for inclusion within existing species, forming three separate clusters in a 16S rRNA gene phylogenetic tree. The isolates, which were obtained from human stools, were Gram-variable or Gram-negative, strictly anaerobic, slightly curved rods; cells from all strains measured approximately 0.5x1.5-5.0 mum and were motile. Two strains belonging to one cluster (A2-181 and A2-183(T)) were the only strains that were able to grow on glycerol and that failed to grow on any of the complex substrates tested (inulin, xylan and amylopectin). Strains belonging to a second cluster (represented by M6/1 and M72/1(T)) differed from the other isolates in their ability to grow on sorbitol. Isolates belonging to a third cluster (L1-83 and A2-194(T)) were the only strains that failed to grow on xylose and that gave good growth on inulin (strains M6/1 and M72/1(T) gave weak growth). All strains were net acetate utilizers. The DNA G+C contents of representative Roseburia strains A2-183(T), A2-194(T), M72/1(T) and R. intestinalis L1-82(T) were 47.4, 41.4, 42.0 and 42.6 mol%, respectively. Based on 16S rRNA gene sequence similarity, three novel Roseburia species are proposed, with the names Roseburia hominis sp. nov. (type strain A2-183(T)=DSM 16839(T)=NCIMB 14029(T)), Roseburia inulinivorans sp. nov. (type strain A2-194(T)=DSM 16841(T)=NCIMB 14030(T)) and Roseburia faecis sp. nov. (type strain M72/1(T)=DSM 16840(T)=NCIMB 14031(T)).