Oropharyngeal colonization with pathogenic organisms contributes to the development of ventilator-associated pneumonia in intensive care units. Although considered basic and potentially nonessential nursing care, oral hygiene has been proposed as a key intervention for reducing ventilator-associated pneumonia. Nevertheless, evidence from randomized controlled trials that could inform best practice is limited. To appraise the peer-reviewed literature to determine the best available evidence for providing oral care to intensive care patients receiving mechanical ventilation and to document a research agenda for this important activity in optimizing patients' outcomes. Articles published from 1985 to 2006 in English and indexed in the CINAHL, MEDLINE, Joanna Briggs Institute, Cochrane Library, EMBASE, and DARE databases were searched by using the key terms oral hygiene, oral hygiene practices, oral care, mouth care, mouth hygiene, intubated, mechanically ventilated, intensive care, and critical care. Reference lists of retrieved journal articles were searched for publications missed during the primary search. Finally, the Google search engine was used to do a comprehensive search of the World Wide Web to ensure completeness of the search. The search strategy was verified by a health librarian. The search yielded 55 articles: 11 prospective controlled trials, 20 observational studies, and 24 descriptive reports. Methodological issues and the heterogeneity of samples precluded meta-analysis. Despite the importance of providing oral hygiene to intensive care patients receiving mechanical ventilation, high-level evidence from rigorous randomized controlled trials or high-quality systematic reviews that could inform clinical practice is scarce.