A 27 bp $tRNA^{Gly}$ region (att1) was identified as the integration site for a 12,384 bp Pfl-derived genomic island containing 15 open reading frames (ORFs) from PA0715 to PA0729 in P. aeruginosa strain PAOl. Homologous island was observed in P. aeruginosa strain PA14, but not in P. aeruginosa strain K (PAK). We isolated the Pfl island from PA14, and determined its 10,657 bp sequences containing 14 ORFs, with significant sequence variations near the borders. In contrast to the PAO1 Pfl island, the PA14 Pfl island was integrated at the 10 bp att2 site between PA1191 and PA1192. The attl site of PA14, however, was still occupied by a third genetic segment, whereas both attl and att2 sites of PAK remained unutilized. These results exemplify an extensive genomic variation of Pfl-related islands involving differential genetic organizations and differential att site utilizations.