OBJECTIVES:  Klebsiella pneumoniae (K. pneumoniae)is a leading cause of nosocomial infections, notably pneumonia, urinary tract infections and blood stream infections. Aim of the study is to analyze the clinical outcome and cost of hospitalization in patients with blood stream infections caused by K. pneumoniae. METHODS:  A retrospective study, involving patients with positive blood cultures for K. pneumoniaewas performed in order to assess the health care costs and the outcomes of extended spectrum beta lactamase (ESBL) production from nosocomial blood stream infections RESULTS: The study included a total of 111 episodes of infection consisting of 69 (62.2%) ESBL-producing and 42 (37.8%) ESBL-nonproducing isolates. Total length of stay (LOS) in hospital and the LOS in hospital before infection was significantly longer for ESBL-producing K. pneumoniaeinfections (p<0.05). Thirty-day mortality was 17 (24.6%) for ESBL-producers and 5 (11.9%) for ESBL-nonproducers (p>0.05). Median total hospitalization cost was 5851,9€ for ESBL- producers and 4192,4€ for nonproducers (p>0.05). CONCLUSIONS: Blood stream infections with ESBL-producing K. pneumonia was associated with longer total LOS in hospital and LOS in hospital before infection where as total hospitalization cost didn’t display any difference. This finding possibly may be attributed to the relatively higher infection related mortality associated with ESBL-producing K. pneumoniae infections.