Nurses are central to the care of older people in hospital. One issue of particular importance to the experience and outcomes of hospitalized older people is their cognitive function. This article reports findings from a focused ethnographic study demonstrating how documentation systems-documents and the social processes surrounding their use-contribute to how nurses come to understand the cognitive function of hospitalized older people. We found that documents contribute to nurses' understanding by serving as a frame of reference, by directing assessments, and by constraining communication. The findings highlight the potential to improve the documents nurses use in hospitals.