Two novel psychrophilic bacterial strains (ZF-6(T) and ZF-8(T)) were isolated from the China No. 1 glacier. Polyphasic taxonomy using physiological and biochemical properties and phylogenetic analysis based on 18S rRNA gene sequences showed that the two isolates belonged to the genus Flavobacterium, and that they were distinct from each other and also from the known species of this genus. Strains ZF-6(T) and ZF-8(T) are Gram-negative and both have an optimal growth temperature of 11 degrees C. Strain ZF-6(T) is able to grow at 0-20 degrees C, the G + C content of its genomic DNA is 34.4 mol% and the major fatty acids of ZF-6(T) are C(16 : 1)omega7c (17.7%) and C15 : 1)omega6c (12.7%). Strain ZF-8(T) showed a strong ability to degrade organic macromolecules such as starch, CM-cellulose, pectin and chitin. Its DNA G + C content is 35.1 mol%, and the major fatty acids are C(16 : 1)omega7C (18.2%) and C(15 : 0) (9.9%). Phylogenetic analysis based on 16S rDNA sequences indicated that ZF-6(T) and ZF-8(T) belong to the genus Flavobacterium and represent two novel species. DNA-DNA hybridization also supported the status of the two new isolates. The names Flavobacterium xinjiangense sp. nov. (type strain, ZF-6(T) = AS 1.2749(T) = JCM 11314(T)) and Flavobacterium omnivorum sp. nov. (type strain, ZF-8(T) = AS 1.2747(T) = JCM 11313(T)) are proposed for the two new isolates.