Evaluation of the nutritional status of surgical patients was carried out by means of cluster analysis of several indicators to identify different nutritional conditions that could be considered frames of reference for the prediction of postoperative infections. Seventy-one surgical patients entered into the first phase of the study that identified four nutritional situations with a different incidence of postoperative sepsis; cluster 1 showed the lowest incidence of infectious episodes, and clusters 2 to 4 were characterized by a higher incidence of sepsis and other complications. In the second phase of the study, 28 patients were examined and compared with the four reference states by means of the determinations of the euclidean distance between the nutritional assessment of the patient and the barycenter of each of the reference states. The incidence of sepsis was similar in the two series of patients, indicating that the characterization of patients in one of the four reference states allows one to predict the risk of postoperative septic complications.