Biochemical, menaquinone, fatty acid and DNA analyses were conducted on a number of streptococci of serological group D. The results indicate that S. faecalis, S. faeclum, S. casseliflavus and taxa previously designated 'S. avium', 'S. durans' and "S. faecalis var. malodoratus' are distinct species. Strains previously labelled 'S. faecium var. mobilis' were shown to be identical with S. casseliflavus. The results also indicate that some group D streptococci recently isolated from chickens constitute a new species.