The outcome of infections occurring at different anatomic sites caused by ESBL-producing E. coli or K. pneumoniae was retrospectively analysed for a 3-y period. 23 cases were compared to 46 controls with infections caused by third-generation cephalosporin-susceptible strains matched by age, severity of illness and duration of hospitalization before onset of infection. Only 27.8% of cases received appropriate empirical antimicrobial therapy compared with 79.6% of controls (OR(paired)=0.053, p=0.001). This did not result in higher costs of antibiotic therapy, a longer median post-infection hospital stay or higher mortality in cases of patients with urinary tract or wound infections. In cases of patients with respiratory tract and bloodstream infections (RTI/BSI), median costs of definitive antibiotic treatment were significantly higher than in controls (325 vs 58.9 Euros, p=0.002). Moreover, more case patients with RTI/BSI had a post-infection stay exceeding the 75th percentile of 15 d on ICU and of 18 d in hospital, respectively (50% vs 6.67%, p=0.034). There was no difference in in-hospital mortality between case and control patients with RTI/BSI (25% vs 20%, p=1.0).