Abstract: Compositions of selected strains of Pseudomonas bacteria having the ability to utilize halogenated aromatic compounds as a sole carbon source are described. The bacteria are isolated from environments where they have been in long association with halogenated aromatic compounds, usually analagous compounds. First L-tryptophan and then a halogenated aromatic hydrocarbon are used as sole carbon sources for isolating and testing the selected strains. The isolated Pseudomonas strains are Pseudomonas putida; Pseudomonas sp. NRRL-B-12,538 or NRRL-B-12,539 or transfer derivatives thereof and are useful for degrading halogenated aromatic pollutants, particularly mono- and di-chloroaromatics.