This study of 198 urban breastfeeding women examined the psychosocial, demographic, and medical factors identified prenatally that may be associated with longer breastfeeding duration and may serve as suitable areas for prenatal breastfeeding promotion interventions. Of 11 psychosocial and demographic factors examined, 5 were important influences on breastfeeding duration: anticipated length of breastfeeding, normative beliefs, maternal confidence, social learning, and behavioral beliefs about breastfeeding. Methods of multivariate linear regression were used to identify prenatal factors that influenced anticipated length. Of the 10 factors entered into the regression model, parity, plans to return to work or school by six months postpartum, and maternal confidence were the most significant factors affecting anticipated length of breastfeeding. Our data suggest several factors amenable to intervention during the prenatal period that appear to influence breastfeeding duration. Prenatal promotion efforts could easily incorporate strategies that influence factors such as normative and behavioral beliefs and maternal confidence.