A bacterial consortium able to degrade the herbicide 4-(2,4-dichlorophenoxy) butyric acid (2,4-DB) was obtained from an agricultural soil of the Argentinean Humid Pampa region which has a history of long-term herbicide use. Four bacterial strains were isolated from the consortium and identified as members of the genera Cupriavidus, Labrys and Pseudomonas. A polyphasic systematic analysis was carried out on strain CPDB6(T), the member of the 2,4-DB-degrading consortium able to degrade 2,4-DB as a sole carbon and energy source. The Gram-negative, rod-shaped, motile, non-sporulating, non-fermenting bacterium was shown to belong to the genus Cupriavidus on the basis of 16S rRNA gene sequence analyses. Strain CPDB6(T) did not reduce nitrate, which differentiated it from the type species of the genus, Cupriavidus necator; it did not grow in 0.5-4.5 % NaCl, although most species of Cupriavidus are able to grow at NaCl concentrations as high as 1.5 %; and it was able to deamidate acetamide, which differentiated it from all other species of Cupriavidus. DNA-DNA hybridization data revealed low levels of genomic DNA similarity (less than 30 %) between strain CPDB6(T) and the type strains of Cupriavidus species with validly published names. The major cellular fatty acids detected were cis-9-hexadecenoic (16 : 1ω7c) and hexadecanoic (16 : 0) acids. On the basis of phenotypic and genotypic characterizations, strain CPDB6(T) was recognized as a representative of a novel species within the genus Cupriavidus. The name Cupriavidus pampae sp. nov. is proposed, with strain CPDB6(T) (=CCUG 55948(T)=CCM-A-29:1289(T)) as the type strain.