The effects of the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) on breast-feeding behavior have been sometimes found inadequate. The determinants of breast-feeding initiation and duration among WIC participants and nonparticipants were modeled by using retrospective cross-sectional data from the 1988 National Maternal and Infant Health Survey. This study corrects for self-selection bias as far as the data allow, in addition to controlling for parents' ages, education, race, and family income. Findings suggest that prenatal WIC participation, combined with breast-feeding advice, significantly increases the initiation of breast-feeding but does not affect duration. The exact nature of effective breast-feeding advice given prenatally at WIC clinics is unclear and warrants further research.