In time of food shortage, accurate assessment of nutrition status is important so that effective aid may be directed to those in greatest need and, in the future, the impact of this aid on the nutritional situation may be assessed. Using a population proportional sampling method and the index weight for height (which is relatively independent of sex, race, and age) as a criterion of nutritional status, CDC investigators determined that about 10% of the sampled population (aged about 6 months through 6 years) in Mali, Mauritania, Niger, and Upper Volta and over 20% in the sampled population in Chad were severely and acutely undernourished. Apparently younger children were affected first, but as the food shortage became more severe the prevalence of undernourished older children increased. This method of nutrition surveillance has proven itself during a stressful period and should be considered a fundamental tool when rapid assessment of acute undernutrition in children in developing nations is required.