BACKGROUND Routine deflation of the endotracheal tube (ETT) cuff of critically ill patients receiving MV is common in Australia and New Zealand. Literature about ventilatorassociated pneumonia (VAP) and antibiotic use rates with different ETT cuff maintenance practices is lacking. OBJECTIVE To determine the impact of a change in ETT cuff maintenance from a minimal leak technique to pressure manometry on the administration of antibiotics for VAP. METHODS A prospective, pre- post observational study conducted in a metropolitan tertiary referral intensive care unit. We analysed data from 178 patients receiving MV for > 48 hours during 13 weeks of minimal leak test ETT cuff technique (pre-intervention, n = 92) or 13 weeks of cuff pressure manometry (postintervention, n = 86), separated by 3 weeks' "wash-out". METHODS Primary outcome was the number of patients receiving antibiotics for the indication of VAP. Secondary outcomes were incidence of ventilatorassociated surveillance events, lengths of stay (LOSs) and mortality. RESULTS Antibiotics were administered for VAP in 24 patients (26.1%) in the pre-intervention period compared with 11 post-intervention patients (12.8%). The univariate antibiotic administraion rate per 100 ventilation days was 15.3% (95% CI, 12.6%-18.4%) v 6.8% (95% CI, 4.9%- 9.3%), and the incident rate ratio (IRR) was 0.45 (95% CI, 0.31-0.64); P < 0.001). After adjustment for ventilation duration, IRR was 0.55 (95% CI, 0.24-1.27); P = 0.160. The ventilator-associated complication incidence rate was lower in the post-intervention group (11.4% v 16.3%; IRR, 0.70 [95% CI, 0.51-0.95]; P = 0.018). After adjustment for duration of MV, IRR was 0.66 (95% CI, 0.25-1.70); P = 0.387. Antibiotic administration for VAP was associated with increased ICU and hospital LOSs, but not with mortality. CONCLUSIONS ETT cuff pressure manometry is associated with a reduced rate of antibiotic administration for a diagnosis of VAP compared with a minimal leak test technique.