Protein energy malnutrition (PEM) occurs when energy and protein intake do not meet requirements. It has a functional and structural impact and increases both morbidity and mortality of a given disease. The Nutrition Committee of the French Pediatric Society recommends weighing and measuring any child when hospitalized or seen in consultation. The body mass index (BMI) must be calculated and analyzed according to references any time growth kinetics cannot be analyzed. Any child with a BMI below the third centile or -2 standard deviations for age and sex needs to be examined looking for clinical signs of malnutrition and signs orienting toward an etiology and requires having his BMI and height dynamics plotted on a chart. PEM warrants drawing up a nutritional strategy along with the overall care plan. A target weight needs to be determined as well as the quantitative and qualitative nutritional care including its implementation. This plan must be evaluated afterwards in order to adapt the nutritional therapy.