Recent studies have found that poor oral hygiene may foster the colonization of the oropharynx by potential respiratory pathogens in mechanically-ventilated (MV), intensive care unit (ICU) patients. Thus, improvements in oral hygiene in MV-ICU patients may prevent ventilator-associated pneumonia (VAP). The Specific Aims of this investigation are: 1) to organize the necessary infrastructure to develop and perform a pilot clinical trial to evaluate alternative oral hygiene procedures to prevent VAP; 2) to use this organization to perform a pilot clinical trial to determine if the use of oral topical chlorhexidine gluconate (CHX) will prevent dental plaque, oropharyngeal colonization by respiratory pathogens, and VAP in MV-ICU patients. This pilot longitudinal, double blind intervention study will consider the appropriate frequency of delivery of CHX to improve oral hygiene in MV-ICU patients. Preliminary data from these pilot studies will also allow accurate sample size calculations to be made for a large-scale multi-center clinical trial; and 3) to perform molecular epidemiological studies to identify and genetically type bacteria cultured from lower airway secretions of MV-ICU patients with or without VAP and compare them to isolates of the same species from their dental plaque.