The National Survey of WIC Participants III (NSWP-III) is the third iteration in the NSWP study series. This study, conducted approximately every 10 years, is designed to describe state and local agency characteristics, examine participants' characteristics, assess participants' experiences with WIC, and estimate improper payments resulting from certification errors in WIC. Reports 1-3 describe findings on state and local WIC agency operations. Reports 4-7 highlight findings on participant characteristics, retention, experiences, and satisfaction. Lastly, reports 8-10 describe findings on certification errors, denials, and improper payments.