Background. The Ten Steps to Successful Breastfeeding are a set of hospital policies and practices, endorsed by the American Academy of Pediatrics, that support mothers in achieving recommended breastfeeding behaviors. Few hospitals in the United States practice the Ten Steps. This dissertation provides evidence to inform incremental implementation of the Ten Steps to improve breastfeeding practices. Methods. Data are from the Breastfeeding Friendly Healthcare project and the Infant Feeding Practices Study II. A multi-site qualitative study of Breastfeeding Friendly Healthcare hospitals explores the theory of "Organizational Readiness to Change" vis-a-vis implementing the Ten Steps. A quasi-experimental design with multiple-case study methods is used to evaluate of the Breastfeeding Friendly Healthcare project. Data from the Infant Feeding Practices Study are used to examine whether the common practice of not providing the care outlined in the Ten Steps creates a barrier to achieving recommendations for breastfeeding duration. Inverse propensity score weights are used with a parametric survival model using a log-normal distribution to estimate the effects. Results. Baseline factors that may influence a hospital's readiness to implement the Ten Steps organize under the two dimensions for "Organizational Readiness to Change," collective efficacy and collective commitment. The Breastfeeding Friendly Healthcare project resulted in increased achievement of certain Steps: 1 (Policy), 2 (Training), 5 (Teach breastfeeding), and 6 (No supplementation) and increased hospital breastfeeding rates. The Infant Feeding Practices Study II analyses showed that not providing the care in the combination of Steps 4 (Early initiation) and 9 (No pacifiers) resulted in the largest decrease in breastfeeding duration: 11.8 weeks. Not providing other combinations of Steps resulted in decreased duration: Steps 3 (Prenatal education) and 4 (Early initiation)--an 8.6-week decrease; and Steps 4 (Early initiation) and 8 (Hunger cues)--a 5.4-week decrease.