Résumé : A comparative study on the minimal inhibitory concentrations (MIC) of CGP 7174/E, piperacillin, cefotaxime and carbenicillin used against 100 strains of Pseudomonas aeruginosa showed the following data: CGP 7174/E: 1.56 mcg/ml; piperacillin: 3.12 mcg/ml; cefotaxime: 12.5 mcg/ml; carbenicillin: 25 mcg/ml (mean MIC values suggest that CGP 7174/E is the most active). Eleven percent of the Pseudomonas aeruginosa strains were resistant to carbenicillin (MIC > 100 mcg/ml). The minimal inhibitory concentrations of the 3 tested antibiotics (piperacillin, cefotaxime and CGP 7174/E) are 2- to 4-fold higher for these carbenicillin-resistant strains.