Oral health is achieved with adequate nutrition, a properly functioning masticatory apparatus, a flow of saliva, and mechanical cleaning of the oral cavity by artificial means. Interruption of one or more of these factors produces significant changes in the oral cavity, leading to collection of debris and formation of plaque, tartar, dental caries, and periodontal disease. The astute nurse will consider these factors in her overall assessment of the client and will institute in the total plan of care specific nursing measures to prevent, minimize, or reverse changes in the oral cavity. The choice of agents to be used for oral hygiene should be based on a knowledge of their characteristics and function rather than on their convenience of preparation or tradition. The method of implementation should be determined by the client's status mentally and physically, and the frequency of care should be determined by a continued evaluation of the results achieved. Too often in nursing we accept into use agents or methods introduced for care with little or no evidence of their effectiveness, and tend to perpetuate their use because of their convenience or our assumptions that they are beneficial. A review of the literature regarding oral hygiene has helped focus on the areas of agreement as well as on the areas of question regarding the efficacy of the components of oral care: the criteria for assessment, the agents selected, the methods used, and the frequency required. Further scientific inquiry should be done by nurses to build on the knowledge and criteria enumerated--specifically, to define further criteria for assessing changes in the condition of the oral cavity--and to study the effects of various agents on the pH of the mouth.