Pseudomonas putida is chemotactic to a range of organic compounds, including several aromatic compounds. Genes involved in this behavioral response were identified by Tn5 mutagenesis of P. putida PRS2000, resulting in a strain that was nonchemotactic to all chemoattractants tested. Cloning and sequencing of the DNA at the DNA at the Tn5 insertion site revealed a 13-kb region that contained 12 open reading frames, 9 of which are homologous to chemotaxis, flagellar and motility genes in other bacterial species. This indicates that the basic chemotaxis machinery of P. putida is similar to that of other bacterial systems, even though some of the compounds that are sensed as attractants are different.