Despite mounting evidence, a question still exists as to the true clinical relevance of varying degrees of malnutrition, the role of currently measured nutritional parameters in identifying malnutrition and predicting clinical risk in individual patients, and the efficacy of nutritional therapy. This study was designed to document the usefulness of the Prognostic Nutritional Index (PNI) as a predictor of clinical course. The nutritional assessments and clinical records of 328 subjects in a Veterans Administration Hospital were reviewed, PNI and complication rates were determined for each of the subjects, and the data statistically analyzed. The PNI was found to be a useful indicator of malnutrition and predictor of clinical course. The PNI appeared to be a more sensitive index of clinical outcome than did comparison of individual nutritional parameters to accepted norms, although it accounted for only 17% of the information needed to predict clinical course perfectly.