Six Gram-negative, rod-shaped, non-spore-forming bacteria isolated from clinical specimens and water samples were investigated for their taxonomic allocation. On the basis of 16S rRNA gene sequence similarities, these strains (CCUG 35299(T), CCUG 24677A, CCUG 48018, CCUG 49054, CCUG 48700A and CCUG 38318(T)) were shown to belong to the Betaproteobacteria, closely related to Naxibacter alkalitolerans (97.9-98.8 % sequence similarity to the type strain). Chemotaxonomic data (major ubiquinone Q-8; major polyamines hydroxyputrescine and putrescine; major polar lipids phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol; major fatty acids C(16 : 1)omega7c and C(16 : 0), with 3-OH C(10 : 0) and 2-OH C(12 : 0) as hydroxylated fatty acids) supported the affiliation of the isolates to the genus Naxibacter. The results of DNA-DNA hybridization and physiological and biochemical tests allowed both genotypic and phenotypic differentiation of the isolates from the described Naxibacter species. Isolates CCUG 35299(T), CCUG 24677A, CCUG 48018, CCUG 49054 and CCUG 48700A were closely related on the basis of DNA-DNA reassociation experiments and therefore represent a single novel species, for which the name Naxibacter varians sp. nov. is proposed, with the type strain CCUG 35299(T) (=CCM 7478(T)). Strain CCUG 38318(T) represents a second novel Naxibacter species, for which we propose the name Naxibacter haematophilus sp. nov. (type strain CCUG 38318(T) =CCM 7480(T)).