A cohort study was carried out on hospitalized adult non-critically ill patients (January 2003-December 2004) to identify factors associated with the acquisition of multidrug-resistant Pseudomonas aeruginosa (MDR-PA). A total of 246 non-critically patients were included, 162 (66%) who revealed MDR-PA in the first isolate and 84 (34%) who had carbapenem-resistant P. aeruginosa (CR-PA) isolates. Multivariate analysis identified nosocomial acquisition (odds ratio [OR] 2.7, 95% confidence interval [CI] 1.1-6.3), urinary catheter (OR 2.1, 95%CI 1.1-4.3), and the prior use of fluoroquinolones (OR 2.6, 95%CI 1.0-6.7) as independent risk factors associated with MDR-PA acquisition. Our results show that antibiotics, most notably, fluoroquinolones, may play a major role in the emergence of MDR-PA.