Integrons from a clinical strain of Acinetobacter baumannii highly resistant to β-lactams have been analyzed. The largest (2.2 kb) contained three gene cassettes: an aacA4, an open reading frame of 417 nucleotides, and an OXA-type encoding gene. The oxa gene nucleotide sequence differed from that of the oxa-20 in 2 bp, one of the mutations being silent. The nonsilent mutation generated a substitution of glutamic acid for aspartic acid. The new OXA has been named OXA-37.