Background Maintaining oral hygiene is a key component of preventing ventilator-associated pneumonia; however, practices are inconsistent. Objectives To explore how characteristics of institutional guidelines for oral hygiene influence nurses' oral hygiene practices and perceptions of that practice. Methods Oral hygiene section of a larger survey study on prevention of ventilator-associated pneumonia. Critical care nurses at 8 hospitals in Northern California that had more than 1000 ventilator days in 2009 were recruited to participate in the survey. Twenty-one questions addressed oral hygiene practices and practice perceptions. Descriptive statistics, analysis of variance, and Spearman correlations were used for analyses. Results A total of 576 critical care nurses (45% response rate) responded to the survey. Three types of institutional oral hygiene guidelines existed: nursing policy, order set, and information bulletin. Nursing policy provided the most detail about the oral hygiene care; however, adherence, awareness, and priority level were higher with order sets (P < .05). The content and method of disseminating these guidelines varied, and nursing practices were affected by these differences. Nurses assessed the oral cavity and used oral swabs more often when those practices were included in institutional guidelines. Conclusions The content and dissemination method of institutional guidelines on oral hygiene do influence the oral hygiene practices of critical care nurses. Future studies examining how institutional guidelines could best be incorporated into routine workflow are needed.