Long-term mechanical ventilation (MV) is a risk factor for acquisition of bacterial pneumonia because the tracheal tube by-passes the natural mechanisms of airway protection, and particularly epiglottis and trachea-bronchial mucosa. Acute respiratory failure and potential associated organ dysfunctions require that MV patients are sedated and sometimes in strict horizontal supine position. Sedation and conscience alteration do not permit to swallow oro-pharyngeal secretions, and horizontal position favors bacterial colonization and secretions stagnation in the posterior part of the pharynx. These aspects favor iterative inhalation of oro-pharyngeal secretions around the cuff of the tracheal tube. The cuff, which principal objective is to permit the pressurization of lower respiratory tract during the inspiratory phase by preventing air leak around the tracheal tube, allows a certain degree of protection of the tracheal tree against micro-inhalations. Using diagnostic criteria of Ventilator associated pneumonia (VAP) based on distal protected samples, their incidence is around 10 per 1,000 MV-days in medical-surgical ICUs. These VAP are associated to an attributable mortality around 25%. A number of recommendations have been established to prevent VAP occurrence. The 45° semi-recumbent positioning of the patient 's reduces gastro-esophageal reflux and VAP incidence. This result is limited by the fact that a 45° inclination is not routinely obtained in every patients (30° would not give the same result ) and that several studies have shown conflicting results. The continuous suction of the secretions above the cuff is very logical but its efficacy has been challenged, partly because technical failures due to the occlusion of the aspiration system and because gravity prevents the tracheal secretions clearance. The selective decontamination of the digestive tract is effective particularly to prevent early VAP, but is limited by its potential role in the global increase in resistance to antibiotics. Oral decontamination with Chlorhexidine or iodine polyvidon reduce VAP. Using drugs which increases the gastric pH to prevent stress ulcers favors gastric bacterial growth and VAP. Using gastric pro-kinetics or post-pyloric enteral nutrition do not reduce VAP. Alternate prone positioning, has not been proven to improve the outcome of ARDS patients but reduces the incidence of VAP, potentially because it favors pharyngeal drainage through the mouth. The use of heat and moisture exchangers to limit airways drying with ventilation, seems better than heat humidifiers to reduce VAP. Recently, the use of an positive end expiratory pressure (PEEP) was shown to reduce the volume on inhalations around the cuff. Finally, mask ventilation, by preserving upper airways integrity, in those cases it allows a sufficient ventilation replacement, is associated to a substantial reduction in VAP.