The Third National Survey of WIC Participants (NSWP-III) is designed to provide nationally representative estimates of improper payments in the WIC program arising from errors in the certification or denial of WIC applicants, to investigate potential State and local agency characteristics that may correlate with these errors, and to assess WIC participants' reasons for satisfaction or dissatisfaction with the program. The NSWP-III builds on three previous studies and reports spanning several decades.