The puzzle of persistent undernutrition in India is largely explained by open defecation, population density, and lack of sanitation and hygiene. The impact on nutrition of many faecally-transmitted infections, not just the diarrhoeas, has been a blind spot. In hygienic conditions much of the undernutrition in India would disappear. To tackle undernutrition effectively requires the elimination of open defecation and a radical transformation of sanitation and hygiene policies and practices.