Although the incidence of breast-feeding has more than doubled in the United States in recent years, this increase has been less evident among blacks and in lower socioeconomic groups. To understand better this lower incidence, cognitive and personality correlates of breast-feeding were examined in two independent lower-class samples: 137 black inner-city mothers and 50 predominantly white mothers. Ego development, depression, and verbal competence were assessed during the first postpartum year. Only 21.9% of the black sample chose to breast-feed, in contrast with 58.0% of the white sample. Although unrelated to depression and social support, breast-feeding was positively associated with ego level and cognitive ability in both samples. Cognitive ability was assessed using the Peabody Picture Vocabulary Test-Revised, which was found to be valid in relation to maternal and infant characteristics for the black socially disadvantaged sample. When compared using multiple regression analysis, the relation of ego maturity to breast-feeding was generally stronger than that of cognitive ability. Women with more ego maturity may breast-feed because of increased feelings of empathy or nurturance or because they are more attuned to current health advisories and able to deviate from community norms to adopt breast-feeding practices more characteristic of the white middle class.