OBJECTIVES: To determine the proportion of infections caused by extended-spectrum ß-lactamase (ESBL)–producing Klebsiella or Escherichia coli Gram-negative organisms in the pediatric intensive care unit (PICU), and to identify risk factors for these infections. METHODS: A retrospective, single-center chart review of patients admitted to a PICU in a 5-year period with infections caused by Klebsiella species or E coli was completed. Data collected include demographics, length of stay, outcome, and relevant risk factors previously defined in the literature. RESULTS: A total of 110 isolates were cultured from 94 patients. A total of 53% of the isolates were E coli, and the remainder were Klebsiella subspecies. Of the 110 isolates, 13 isolates (11.8%) in 7 patients were ESBL positive. The ESBL-producing isolates were equally distributed amongE coli and Klebsiella and were primarily cultured from tracheal aspirates. Most of the ESBL-positive isolates (9 of 13; 69%) were cultured from patients who received ceftazidime and/or cefotaxime in the preceding 30 days. Patients infected with E coli had higher PRISM 1 scores and were more likely to have a Foley catheter, whereas infections with Klebsiella were more common in mechanically ventilated males. Although not statistically significant, 80% of patients who were infected with non–ESBL-producing organisms survived to hospital discharge versus 57% of those infected with ESBL-producing E coli and Klebsiella. CONCLUSIONS: Almost 12% of E coli and Klebsiella isolates in this patient population tested positive for ESBL production. ESBL production was equally distributed between E coli and Klebsiella species. These organisms were cultured from 7% of the study patients. As reported in previous studies, patients infected with ESBL-producing organisms most often had received prior cephalosporins and had a longer length of stay in the PICU.