Two strains of gram-negative bacteria isolated because of their abilities to decompose xenobiotic compounds were subjected to a polyphasic taxonomic study. On the basis of 16S rRNA gene sequence analysis, the two strains were found to belong to the genus Pseudomonas. Benzene degrading strain DSM 8628(T) was moderately related to P. flavescens NCPP 3063(T) (98.3% similarity), P. monteilii CIP 104883(T), and P. plecoglossicida FPC 951(T) (98.1%). Strain DSM 9751(T) capable to grow with cetyltrimethylammonium chloride as the sole carbon source showed the highest similarity values with P. tremae CFBP 2341(T) and P. meliae MAFF 301463(T) (98.0%), both related to Pseudomonas syringae. The fatty acid pattern of strain DSM 8628(T) was distinct from patterns of other members of the genus Pseudomonas in combining a high ratio of 3OH-C(12:1) (5.1%), a low ratio of 2OH-C(12:0) (0.2%) and a relatively low ratio of C(18:1)omega7c (23.8%). On the basis of phylogenetic analysis, physiological properties and the composition of whole cell fatty acids, two novel species, Pseudomonas benzenivorans sp. nov. with the type strain DSM 8628(T) (=CIP 109857(T)) and Pseudomonas saponiphila sp. nov. with the type strain DSM 9751(T) (=CIP 109856(T)), are proposed.