The impact of high level cephalosporin resistance due to Enterobacteriaceae harbouring a type I-inducible chromosomal b-lactamase on the outcome of ventilator-associated pneumonia (VAP) remains unknown. A retrospective cohort study was conducted in two intensive care units (ICUs) over a four-year period to identify factors prognostic of VAP caused by high level AmpC (HL-AmpC)-producing Enterobacteriaceae. The study included 75 patients, who developed VAP due to Enterobacteriaceae harbouring a type I-inducible chromosomal b-lactamase. One-third of these VAP episodes were due to HL-AmpC-producing Enterobacteriaceae. Demographic and clinical characteristics at ICU admission were similar for patients, regardless of Enterobacteriaceae susceptibility, but those who developed VAP due to HL-AmpC-producing Enterobacteriaceae received antibiotics more frequently before its onset and had higher disease severity and organ dysfunction scores. Enterobacter spp. were the major HL-AmpCproducing micro-organisms responsible for VAP. VAP due to HL-AmpC-producing Enterobacteriaceae is rare. High level cephalosporin resistance was not associated with higher day 28 mortality, despite its association with more severe disease at VAP onset.