Dehydration has serious consequences for older adults, including increased risk of illness or death. This retrospective review of medical records describes the prevalence, assessment, and risk factors for chronic dehydration in 185 older adults who visited an emergency department in June 2000. Results showed chronic dehydration was present in 89 (48%) patients. Physicians documented assessment for signs of dehydration in 23 (26%) of the dehydrated older adults, but no independent assessments for dehydration were recorded by nurses. These findings indicate many older adults may suffer from unrecognized dehydration, and nurses should be alert to the possibility that dehydration may be present in community-dwelling older adults as well as those who live in residential facilities.