This paper synthesizes the academic and professional literature about participation in the Women, Infants and Children (WIC) Program in the United States. First, we compile evidence about differences in enrollment, perceptions, and experiences by eligible populations (women, infants, children) and by social categories (e.g., race, educational attainment, immigration status). Second, we describe barriers to participation through a twofold typology: operational and systemic. Operational barriers concern the perceived hassle of several aspects of WIC, and systemic barriers involve issues of stigma, fear, access, and language.