Two anaerobic, non-spore-forming, bacteria (YIT 11850(T) and YIT 11860(T)) that stained Gram-negative, were isolated from human faeces. Cells of strain YIT 11850(T) were coccobacilli, asaccharolytic and largely unreactive, with only traces of lactate and propionate as metabolic end products; however, strain YIT 11850(T) was able to decarboxylate succinate to propionate. The DNA G+C content of strain YIT 11850(T) was 51.9 mol%. Following 16S rRNA gene sequence analysis, this strain was found to be most closely related to Dialister propionicifaciens, with 95.1 % sequence similarity between the two taxa. Biochemical data supported the affiliation of strain YIT 11850(T) to the genus Dialister. Strain YIT 11850(T) therefore represents a novel species for which the name Dialister succinatiphilus sp. nov. is proposed; the type strain is YIT 11850(T) (=DSM 21274(T)=JCM 15077(T)). Cells of the other isolate, strain YIT 11860(T), were non-motile, rod-shaped, positive for aesculin hydrolysis, negative for indole production, produced succinic and acetic acids as end products of glucose metabolism and possessed a DNA G+C content of 45.5 mol%. On the basis of 16S rRNA gene sequence similarity values, this strain was shown to belong to the family 'Porphyromonadaceae' related to Barnesiella viscericola (96.0 %); similarity values with species within the family 'Porphyromonadaceae' with validly published names were less than 86 %. Biochemical data supported the affiliation of strain YIT 11860(T) to the genus Barnesiella. Strain YIT 11860(T) therefore represents a novel species for which the name Barnesiella intestinihominis sp. nov. is proposed; the type strain is YIT 11860(T) (=DSM 21032(T)=JCM 15079(T)).