In spite of the many anthropometric, biohumoral, and immunologic parameters employed in the nutritional assessment of hospitalized patients, it is difficult in clinical practice to evaluate accurately the degree and type of malnutrition and to assess the prognostic significance of this determination. The purpose of this study is to evaluate nutritional status of surgical patients by means of cluster analysis in orderr to identify different nutritional patterns and to evaluate their clinical and prognostic significance. Nutritional assessment of 71 surgical patients was carried out at admission, and the sets of data were evaluated by means of cluster analysis. Four clusters with different nutritional patterns were identified. The incidence of clinical variables (type of disease, postoperative sepsis, palliative procedures, mortality at 6 months, etc.) in each cluster was determined in order to evaluate their clinical and prognostic significance. Cluster 1 showed minor variations of the indicators, including most of the controls presented the lowest incidence of sepsis, palliative procedures, and mortality at 6 months. It was then considered as a reference group representative of the normal nutritional condition at our institution. The other three clusters showed major variations of nutritional indicators and represent poorer risk clinical conditions. Sepsis, palliative procedures and mortality rate were significantly more frequent in these clusters (p less than 0.05, p less than 0.001, p less than 0.05). A different distribution in the clusters was recorded in gastrointestinal tract cancers and other neoplasms. Only the incidence of gastrointestinal tract cancers increases progressively in the clusters with poorer prognosis, suggesting that this type of neoplasia is more frequently associated with major changes of nutritional status.