The uvrB gene of Pseudomonas aeruginosa has been isolated from a genomic library by complementation of an Escherichia coli uvrB mutant. The complete nucleotide sequence of P. aeruginosa uvrB consists of 2,013 bp. encoding a polypeptide of 670 amino acids. A P. aeruginosa SOS consensus region, which functions as a binding site for the LexA repressor molecule, is not present in the upstream region of the uvrB gene isolated. By transcriptional fusions with a reporter gene, it has been demonstrated that, contrary to what happens with the homologous gene of E. coli, the P. aeruginosa uvrB gene is not DNA damage inducible. Nevertheless, the UvrB protein must be functional in P. aeruginosa cells because a uvrB-defective mutant is extremely sensitive to UV radiation.