Maternal self-efficacy for breast-feeding may contribute to success in breast-feeding. This study aimed to increase breast-feeding self-efficacy and actual breast-feeding through an intervention based on Bandura's self-efficacy theory. A total of 90 pregnant women participated in the study. The women who were assigned to a breast-feeding self-efficacy intervention showed significantly greater increases in breast-feeding self-efficacy than did the women in the control group. Furthermore, at 4 weeks postpartum, women in the intervention group showed a trend toward breast-feeding their infants longer and more exclusively than did those in the control group. Greater increases in breast-feeding self-efficacy were associated with a significantly higher level of breast-feeding. Replicating previous research, breast-feeding self-efficacy was significantly related to concurrent breast-feeding behavior, and high antenatal breast-feeding self-efficacy predicted a higher level of later breast-feeding in control-group women. These findings have implications for breast-feeding support programs and for the potential general utility of self-efficacy-based interventions in health education. (Contains 1 table.)