Minimal inhibitory concentrations (MICs) against piperacillin/tazobactam were determined on a total of 50 clinical isolates of imipenem resistant Pseudomonas aeruginosa (IRPA). MIC₅₀ and MIC₉₀ were 32μg/mL and 512μg/mL, respectively. The susceptibility of IRPA against piperacillin/tazobactam was 59%. Of the 50 IRPA strains, only two were PCR positive for bla_VIM and none for bla_IMP. (Korean J Clin Microbiol 2007;10:171-172)