Human milk is the natural nutrition for all infants. According to the American Academy of Pediatrics (AAP), it is the preferred choice of feeding for all infants. The goals of Healthy People 2010 for breastfeeding are initiation rate of 75% and continuation of breastfeeding of 50% at 6 months and 25% at 12 months postpartum. A survey of US children in 2002 indicated that 71% had ever been breastfed. The percentage of infants who continued to breastfeed to some extent are 35% at 6 months and 16% at 12 months. Although the breastfeeding initiation rate from this survey is close to the goal of 75%, the breastfeeding continuation rates at 6 and 12 months are short of the goals set by that of Healthy People 2010. Tufts-New England Medical Center Evidence-based Practice Center completed a review in 2006 examining the effects of breastfeeding on infant and maternal health outcomes in developed countries. The Center on Primary Care, Prevention and Clinical Partnerships at the Agency for Healthcare Quality and Research (AHRQ), on behalf of the US Preventive Services Task Force (USPSTF), requested an additional related evidence report on the effectiveness of interventions to promote breastfeeding. The topic, effectiveness of interventions to encourage and support breastfeeding, was last considered in 2003 by the USPSTF. The Task Force issued a B recommendation (fair evidence that the service improves important health outcomes) for structured education and behavioral counseling programs to promote breastfeeding, and an I recommendation (insufficient evidence to recommend for or against routinely providing the service) for other interventions. The present report will be used by the USPSTF to update its 2003 recommendation. According to AAP, some of the obstacles to initiation and continuation of breastfeeding include insufficient prenatal education about breastfeeding, disruptive maternity care practices, and lack of family and broad societal support. Effective interventions reported to date include changes in maternity care practices, like those implemented in pursuit of the Baby Friendly Hospital Initiative designation, and worksite lactation programs. Some of the other interventions implemented include peer to peer support, maternal education and media marketing. This review focuses only on interventions that were initiated in a primary care setting. Any counseling or behavioral intervention initiated from a clinician's practice (office or hospital) to improve breastfeeding initiation, duration, or both will be considered. Interventions could be conducted by a variety of providers (lactation consultants, nurses, peer counselors, midwives or physicians) in a variety of settings (hospital, home, clinic, or elsewhere) as long as they originated from a health care setting. Health care system interventions, such as staff training, will also be included.