The Strengthening Partnerships, Results, and Innovations in Nutrition Globally (SPRING) Project and the Pan American Health Organization identified the need for a core set of key practices that characterize the diet and feeding practices associated with good nutrition among adolescent girls, women, and pregnant and breastfeeding women. This is one of two papers commissioned to provide the relevant scientific and programmatic background to begin to address this goal. This paper summarizes existing information on the current nutritional status of adolescent girls, women of reproductive age, and pregnant and lactating women in low- and middle-income countries.