We have confirmed that malnutrition is very frequent in hospitalized patients. There is no agreement about which are the indexes or criteria agreement about which are the indexes or criteria that can be used to define malnutrition, specially in early stages. In the present work, we have studied 100 patients randomly chosen amongst the admissions that occurred in the Internal Medicine Department over a period of one year. The patients were submitted to a protocol which included the following: anthropometric measurements, seric proteins and routine determinations (sugar level, cholesterol, uric acid, etc.) It has been considered as malnourished those patients who presented some marker with a value lower than 90% of the standard value. According to these criteria, 25 of them had a caloric-protein malnutrition, 24 had a proteic malnutrition and 25 of them had mixed malnutrition. The most sensible parameters had been the triceps skin fold and retinal transporting protein.