The genus Enhydrobacter, first reported as a member of the family Vibrionaceae, has been placed in the family Moraxellaceae, but as a genus incertae sedis in Bergey's Manual of Systematic Bacteriology 2nd edition. During our taxonomic investigation of Enhydrobacter-like organisms, we observed that the 16S rRNA sequences of E. aerosaccus-type strain versions NCIMB 12535(T) , ATCC 27094(T) and CCUG 58314(T) were very different from the accessible data (accession no. AJ550856). Phylogenetic analysis of our 16S rRNA sequence data revealed that these organisms were located within the family Rhodospirillaceae. The genera Inquilinus, Oceanibaculum, Skermanella and Nisaea were closely related (sequence similarities were 88.3~87.0%), but Enhydrobacter could be distinguished from these genera by growth characteristics, fatty acid profiles (C(19:0) cyclo �s8c; 38.4% C(18:1) �s7c; 32.2%, and C(16:0) ; 8.9% were major components), in being non-flagellated, and differing in enzymatic activities, including trypsin and �]-glucosidase. From these data, we conclude that the genus Enhydrobacter should be recognized as an independent genus of the family Rhodospirillaceae within the class Alphaproteobacteria.