|Detailed Objective: This study will revise methods of using survey data to estimate WIC eligibility and participation patterns, focusing on infants less than 1 year old, and methods to examine outcomes for WIC infants and children. In previous work, the estimated number of infants and postpartum women who participate in WIC exceeds the estimated number of people eligible for the program by as much as 20 to 30 percent. These high coverage rates have led some to speculate that some WIC participants are ineligible. However, a recent National Academy of Sciences (NAS) panel on WIC eligibility concluded that the methods that resulted in these estimates had limitations, in particular, that they were likely to understate the number of people eligible for the program. To address these issues, this project will revise and refine research on WIC eligibility and participation patterns in survey data, looking particularly at infants less than one year of age. The project will extend the research by examining outcomes for WIC infants and children. In particular, it will examine anthropometric measures (height and weight) of infants and children and grapple with modeling the fundamental issue of possible self-selection into the WIC program that may bias parameter estimates.