A case-control study was performed to find the risk factors in the acquisition of extended-spectrum beta-lactamase (ESBL) Klebsiella pneumoniae. From 1 May 2001 to 30 September 2001, 422 isolates ofK. pneumoniae identified by the microbiological laboratory in Hsin-Chu hospital were collected, 59 of which were ESBL-producing strains. The prevalence rate was 14% (59/422). There were 43 case patients (ESBL-producing K. pneumoniae) and 86 controls (non-ESBL-producing K. pneumoniae). Tracheostomy, insertion of a Foley catheter, endotracheal tube, nasogastric tube and central venous catheter were found to be risk factors in the acquisition of K. pneumoniae with ESBLs by univariate analysis. Tracheostomy (odds ratio, 5.13; 95% CI, 1.24-21.1;P =0.023) and ceftazidime use (odds ratio, 13.40; 95% CI, 1.21-148.85; P=0.035) remained as risk factors by multivariate analysis with logistic regression. Other anti-pseudomonal agents should be used as empirical therapy to treat possible Pseudomonas aeruginosa infection in order to reduce ceftazidime use and thereby decrease the prevalence of ESBL producing strains of Enterobacteriaceae.