BACKGROUND: Pneumonia occurring in residents of long-term care facilities and nursing homes can be termed 'nursing home-acquired pneumonia' (NHAP). NHAP is the leading cause of mortality among residents. NHAP may be caused by aspiration of oropharyngeal flora into the lung, and by failure of the individual's defence mechanisms to eliminate the aspirated bacteria. Oral care measures to remove or disrupt oral plaque might be effective in reducing the risk of NHAP. OBJECTIVES: To assess effects of oral care measures for preventing nursing home-acquired pneumonia in residents of nursing homes and other long-term care facilities. SEARCH METHODS: Cochrane Oral Health's Information Specialist searched the following databases: Cochrane Oral Health's Trials Register (to 15 November 2017), the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library, 2017, Issue 10), MEDLINE Ovid (1946 to 15 November 2017), and Embase Ovid (1980 to 15 November 2017) and Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1937 to 15 November 2017). The US National Institutes of Health Trials Registry (ClinicalTrials.gov) and the World Health Organization International Clinical Trials Registry Platform were searched for ongoing trials. No restrictions were placed on the language or date of publication when searching the electronic databases. We also searched the Chinese Biomedical Literature Database, the China National Knowledge Infrastructure, and the Sciencepaper Online to 20 November 2017. SELECTION CRITERIA: We included randomised controlled trials (RCTs) that evaluated the effects of oral care measures (brushing, swabbing, denture cleaning mouthrinse, or combination) in residents of any age in nursing homes and other long-term care facilities. DATA COLLECTION AND ANALYSIS: At least two review authors independently assessed search results, extracted data, and assessed risk of bias in the included studies. We contacted study authors for additional information. We pooled data from studies with similar interventions and outcomes. We reported risk ratio (RR) for dichotomous outcomes, mean difference (MD) for continuous outcomes, and hazard ratio (HR) for time-to-event outcomes, using random-effects models. MAIN RESULTS: We included four RCTs (3905 participants), all of which were at high risk of bias. The studies all evaluated one comparison: professional oral care versus usual oral care. We did not pool the results from one study (N = 834 participants), which was stopped at interim analysis due to lack of a clear difference between groups.We were unable to determine whether professional oral care resulted in a lower incidence rate of NHAP compared with usual oral care over an 18-month period (hazard ratio 0.65, 95% CI 0.29 to 1.46; one study, 2513 participants analysed; low-quality evidence).We were also unable to determine whether professional oral care resulted in a lower number of first episodes of pneumonia compared with usual care over a 24-month period (RR 0.61, 95% CI 0.37 to 1.01; one study, 366 participants analysed; low-quality evidence).There was low-quality evidence from two studies that professional oral care may reduce the risk of pneumonia-associated mortality compared with usual oral care at 24-month follow-up (RR 0.41, 95% CI 0.24 to 0.72, 507 participants analysed).We were uncertain whether or not professional oral care may reduce all-cause mortality compared to usual care, when measured at 24-month follow-up (RR 0.55, 95% CI 0.27 to 1.15; one study, 141 participants analysed; very low-quality evidence).Only one study (834 participants randomised) measured adverse effects of the interventions. The study identified no serious events and 64 non-serious events, the most common of which were oral cavity disturbances (not defined) and dental staining.No studies evaluated oral care versus no oral care. AUTHORS' CONCLUSIONS: Although low-quality evidence suggests that professional oral care could reduce mortality due to pneumonia in nursing home residents when compared to usual care, this finding must be considered with caution. Evidence for other outcomes is inconclusive. We found no high-quality evidence to determine which oral care measures are most effective for reducing nursing home-acquired pneumonia. Further trials are needed to draw reliable conclusions.