Malnutrition affects a high number of hospitalized patients and worsen their outcome. Nutritional support is then essential and the appropriate way is in the most cases represented by dietary supplementation or enteral feeding. Parenteral nutrition may be required in some cases of particularly severe malnutrition. Its efficiency is widely proved and parenteral nutrition provides an adequate nutritional support when oral or enteral nutrition is impossible or insufficient. The energy supply by a mixture of nutrients in multicompartiment bags is now routinely accepted and all-in-one mixtures facilitate home parenteral nutrition. The strict respect for indications and for procedures during use should reduce the parenteral nutrition-induced complications. The benefits of this therapy are obtained with a carefully trained team but the most undernourished patients should not be deprived of its advantages.