Technical Abstract: Human milk is recognized by the American Academy of Pediatrics as the optimal feeding for all infants, although supplementation with specially formulated human milk fortifiers is required to meet the nutritional needs of premature newborns. Exclusive breastfeeding is recommended for the first six months after birth, and partial breastfeeding for at least 12 months, and thereafter for as long as mutually desired. The World Health Organization advises that partial breast feeding continue for up to two years, and beyond. Despite these recommendations, breastfeeding is initiated by only 66 percent of women in the United States and continued for six months by 22 percent. Goals for Healthy People 2010 include increasing the proportion of women who initiate breastfeeding and continue for six months to 75 and 50 percent, respectively. The Economic Research Service of the US Department of Agriculture estimates that achievement of this goal would result in annual savings of over 3.6 billion dollars due to reductions in infant morbidity. Breastfeeding in the perinatal period is reviewed here. The physiology of lactation, maternal nutrition during lactation, and complications of breastfeeding are discussed separately.