To assure the continued success of the WIC, Congress mandated that the Food and Nutrition Service of the U.S. Department of Agriculture (USDA) reevaluate the program's food packages every 10 years. In 2014, the USDA asked the Institute of Medicine to undertake this reevaluation to ensure continued alignment with the goals of the Dietary Guidelines for Americans. This, the second report of this series, provides a summary of the work of phase I of the study, and serves as the analytical underpinning for phase II in which the committee will report its final conclusions and recommendations.