Breastfeeding is the recommended feeding method for infants. The decision to allow women to breastfeed while consuming alcohol and other drugs postpartum presents a problem for the health care provider. This article discusses the biochemical properties of various drugs as they relate to breastfeeding. Women in a methadone treatment program should be allowed to breast feed; however, more research is needed to determine the efficacy of breastfeeding when women are receiving buprenorphine. Breastfeeding should not be recommended in women who abuse heroin recreationally until more information is known about the actual amount of morphine present in the breast milk.