Pseudomonas sp. OX1, an aromatic compound-degrading bacterium that was tentatively identified by conventional biochemical methods as P. stutzeri, has now been investigated at the molecular level to clarify its taxonomic position. Amplified ribosomal DNA restriction analysis and multiple enzyme restriction fragment length polymorphism (MERFLP) analysis suggested that Pseudomonas sp. OX1 could not be classified as P. stutzeri. Phylogenetic analyses based on 16S rRNA and gyrB genes further confirmed that this strain belongs to the Pseudomonas (sensu stricto) genus, but not to the stutzeri species. The data obtained demonstrated that Pseudomonas sp. OX1 belongs to intrageneric cluster II and is related to the P. fluorescens-P. syringae complex.