OBJECTIVES: Urinary tract infections (UTIs) caused by extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae are on the increase. Although cefmetazole is stable in vitro against the hydrolyzing activity of ESBLs, no clinical study has ever evaluated its role in infections caused by these organisms. We therefore evaluated the efficacy of cefmetazole compared to carbapenems against pyelonephritis caused by ESBL-producing Enterobacteriaceae. METHODS: A retrospective chart review was conducted at a tertiary care hospital from August 2008 to July 2010. Chart reviews were done for patients with ESBL-producing organisms in urine identified in the microbiology database. Patients who were treated with cefmetazole were compared to those treated with carbapenems. The clinical and bacteriological cure rates at 4 weeks after completion of therapy were evaluated. RESULTS: Two hundred and fifty-six urine cultures growing ESBL-producing organisms were identified during the study period. Ten patients treated with cefmetazole and 12 patients treated with carbapenems were evaluated. There was no difference in clinical (9/10 vs. 12/12, p=0.46) or bacteriological cure rate (5/7 vs. 6/7, p=1.00) at 4 weeks after the completion of therapy. There was no difference in the incidence of adverse effects (2/10 vs. 2/12, p=1.00). CONCLUSIONS: Cefmetazole may be a useful option for the treatment of UTIs caused by ESBL-producing organisms. Prospective and larger sized studies are needed to confirm our findings.