Seventeen strains of Cytophaga, Flavobacterium and Actinobacillus species were taxonomically characterized. DNA base composition of these strains ranged from 39.0 to 42.3mol%, and the menaquinone system was MK-7. All the strains contained sphingolipids with long-chain bases, which are characteristic of the genus Sphingobacterium. Based on their chemotaxonomic and physiological characteristics together with DNA/DNA hybridization studies, we propose two new species and two new combinations, Sphingobacterium faecium sp. nov., Sphingobacterium piscium sp. nov., Sphingobacterium heparinum comb. nov., Sphingobacterium thalpophilum comb. nov. and two genospecies of the genus Sphingobacterium. Flavobacterium yabuuchiae was found to be a synonym of Sphingobacterium spiritivorum.