The factors that influence the actual initiation and duration of breastfeeding were studied among low-income women followed by the Canada Prenatal Nutrition Program (CPNP). A group of 196 pregnant women were selected at random from a sample of 6223 pregnant women who registered with the CPNP. Two 24-hour recalls and information regarding lifestyle habits, peer support, and infant-feeding practices were obtained between 26 and 34 weeks of gestation and 21 days and 6 months after birth. Women who received a university education (completed or not completed) versus women with < or = high school education (odds ratio [OR], 8.40; 95% confidence interval [CI], 1.02-69.50), women born outside Canada (OR,8.81; 95% CI, 3.34-23.19), and women of low birth weight infants (OR, 0.39; 95% CI, 0.16-0.96) were more likely to initiate breastfeeding. Late introduction of solid foods (P = .004), nonsmoking (P = .005), multiparity (P = .012), and a higher level of education (P = .049) were positively associated with the duration of breastfeeding among initiators. Understanding factors associated with initiation and duration of breastfeeding among low-income women is critical to better target breastfeeding promotion.