Olsen I. Chemotaxonomy of bacteroides: a review. Acta Odontol Scand 1994;52:354-367. Oslo. ISSN 0001-6357.The loose definition ofBacteroides, some species of which are important etiologic agents of oral diseases, has enabled isolates with only marginal similarities to be reposited in this genus. Many attempts have been made over the years to improve the taxonomy of this heterogeneous group of bacteria. The present article reviews major chemotaxonomic characters and techniques that have been used for this purpose: pigmentation, metabolites, whole-cell fatty acids, phospholipids, isoprenoid quinones, carbohydrates of lipopolysaccharide, whole-cell proteins, peptidoglycans, enzymes, pyrolysis mass spectrometry, DNA composition, restriction fragment length polymorphisms of DNA and ribosomal (r) RNA, homology of DNA and NNA, DNA-rRNA hybridization, and 16s and 5s rRNA oligonucleotide cataloging and sequencing. Despite improvements in their taxonomy, some bacteroides are still misclassified. Suggestions for further improvements in the taxonomy of bacteroides are made.