The MAL-ED study aimed to understand the complex relationships between enteric infections, malnutrition, gut physiology, physical growth, cognitive development, and immune responses in infants and children in resource-poor environments. The study was conducted across eight countries: Bangladesh, India, Nepal, Pakistan, Brazil, Peru, South Africa, and Tanzania. Participants were recruited through local community services and events. Around 200 mother-infant dyads were recruited from each of the eight study sites between 2009 and 2012 within 17 days of the infant's birth. Each child and mother pair was assessed twice weekly during the first two years of life. Each child was visited once a quarter at a minimum between three and five years of age.