A prospective analytic study was conducted to examine the influences of the social network on the choice and duration of breast-feeding among 125 mothers of preterm infants. The Influence of Specific Referents (ISR) Scale was used to measure mothers' perceptions of the wishes of seven social referents regarding feeding choice and to assess mothers' motivation to comply with their referents' wishes. Referents included family members, friends, and health care professionals. Mothers choosing to breast-feed reported greater influence from referents than those choosing to formula-feed. Among the 88 mothers who initiated breast-feeding or expression, the number of supports reported by mothers was the most influential factor on duration of lactation. Women with no source of support were six times more likely to cease lactation than women with six sources of support.