Theory suggests that the decision to return to employment after childbirth and the decision to breast-feed may be jointly determined. We estimate models of simultaneous equations for two different aspects of the relationship between maternal employment and breast-feeding using 1993-1994 data from the U.S. Food and Drug Administration’s Infant Feeding Practices Study. We first explore the simultaneous duration of breast-feeding and work leave following childbirth. We find that the duration of leave from work significantly affects the duration of breast-feeding, but the effect of breast-feeding on work leave is insignificant. We also estimate models of the daily hours of work and breast-feedings at infant ages 3 months and 6 months postpartum. At both times, the intensity of work effort significantly affects the intensity of breast-feeding, but the reverse is generally not found. Competition clearly exists between work and breast-feeding for many women in our sample.