The present article reviews the strengths and weaknesses of the three main methods for estimating the prevalence of malnutrition in populations: self-reported hunger, estimates based on food supplies, and anthropometrics. Although far from flawless, anthropometrics is found to be the most reliable method and also the most useful for directing policy. The main form of malnutrition among adults is overweight, not only in developed countries, but also in almost all developing countries. Only in a few developing countries is adult underweight more prevalent. By the conventional anthropometric indicators, about one-quarter of all children below the age of 5 in the developing countries are stunted or underweight, and about 10% are wasted. The total burden of malnutrition among young children, as measured by the Composite Index of Anthropometric Failure, is considerably higher, about 60% in India, the country with the largest child population in the world.