Nosocomial Klebsiella pneumoniae infection is associated with a high mortality in neonates and antimicrobial therapy of these infections has been complicated by the emergence of multiresistant strains. These organisms remain susceptible to only a few antimicrobial agents, and some of these are not recommended for use in children. In this study the antimicrobial agents used in the treatment of 33 neonates with Klebsiella pneumoniae (K. pneumonia) infection in our tertiary neonatal unit, during an outbreak were: piperacillin/tazobactam (13), imipenem/cilastatin (17), cefotaxime (2), and ciprofloxacin (1). Extended-spectrum beta-lactamase production was detected in K. pneumoniae isolates from 18 of 33 (54.5%) neonates. All-cause mortality was 13 of 33 (39.4%) and there was no significant difference in mortality between neonates treated with imipenem/cilastatin (6 of 17 or 35.3%) and neonates treated with piperacillin/tazobactam (6 of 13 or 46.2%). The duration of antimicrobial therapy and total hospital stay was similar between neonates who received imipenem/cilastatin and those that received piperacillin/tazobactam. This report suggests that piperacillin/tazobactam may be a useful antimicrobial agent in neonatal infections caused by beta-lactamase-producing organisms.