Human milk is the optimal nutrition for infants for the first six months of life. Healthy People 2010 includes national breastfeeding goals including 75% of women initiating breastfeeding, 50% continuing for at least six months, and 25% continuing for at least one year. The American Academy of Pediatrics recommends exclusive breastfeeding for six months, with continued breastfeeding for at least one year or as long as mutually desired by mother and child. In the United States, those who least likely to breastfeed are women who are African American, residents of the southeast, and WIC participants. This dissertation examines patterns and correlates of breastfeeding practices among North Carolina WIC clients from 1996 through 2002. Because both macro- and micro-level factors can influence breastfeeding, the social ecological model is used as a theoretical framework to guide both papers. Beginning with an assessment of breastfeeding initiation and early introduction of human milk substitute (HMS) in the first paper, and following with an intent-to- treat evaluation of an in-home postpartum breastfeeding support program, this dissertation attempts to identify individual and community factors associated with breastfeeding. Results indicate that breastfeeding initiation has increased over time, but so has introduction of HMS within the first week postpartum among WIC clients who initiated breastfeeding. There are several practice and public health implications of the findings, including recommendations related to hospital policies, WIC breastfeeding support, breastfeeding interventions, and evaluation methodologies.