There is a tremendous gap in the information available to support the practice of hospital-based dietitians and to address the issue of how the risk of developing protein-energy malnutrition can be avoided in the majority of patients. This article describes the rationale and benefits of creating a nutrition registry of within-hospital clinical nutrition care. A nutrition registry is made up of observational data, collected on an ongoing basis, of nutritional interventions provided to hospitalized patients. It is the first step in data gathering to demonstrate the effectiveness of clinical nutrition interventions. The methods and preliminary results of a nutrition registry that was established at The University of Illinois Medical Center, Chicago, ill, are presented. Using subjective global assessment, 55% (257 of 467) of patients at admission and 60% (280 of 467) of patients at discharge were moderately or severely malnourished. Patients that were normal nourished at admission and became moderately or severely malnourished had higher hospital charges ($40,329 for moderately malnourished patients, $76,598 for severely malnourished patients) than those that remained normal nourished ($28,368). This pattern held independent of admission nutritional status. Major challenges in implementation of a registry into the responsibilities of the staff dietitian are reviewed. The established and will provide the much needed baseline data conclusion of this study is that nutrition registries can to document the impact of nutrition interventions on outcomes of medical care.