USDA’s Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) provides nutritious foods, nutrition counseling, and referrals to health and other social services to low-income women and their infants/children up to age 5. Despite the health benefits of WIC participation, many eligible women do not participate during pregnancy, and many households exit WIC when a participating child turns 1 year old. The authors of this report use the first two waves of the Early Childhood Longitudinal Study-Birth Cohort (ECLS-B) to understand these transitions into and out of WIC. Findings show that households that are more economically advantaged are more likely to delay entry into the program or exit after a child turns 1 year old. Some of the mothers exiting the program reported that WIC requires too much effort and that its benefits are not worth the time (26.2 percent of those exiting) or that they have scheduling and transportation problems (almost 10 percent of those exiting), suggesting that the costs of participation may be a barrier to continued WIC participation.