['Multiple datasets collect breastfeeding data in the United States (US), but a coordinated monitoring and surveillance system does not currently exist. The Special Supplemental Nutrition Program for Women, Infants and Children (WIC) reaches over 50% of all infants in the US and provides a potential wealth of administrative data about the breastfeeding practices of low-income women.', 'The objective of this research was to assess whether WIC administrative data are a valid source of information about breastfeeding practices.', 'A phone survey of 2015 postpartum WIC mothers in Southern California was conducted to assess the feeding practices of mothers with infants 2-12 months old. Survey data were linked with WIC administrative records from the same month in order to assess the percent agreement between feeding behavior as reported by survey methods and as documented in WIC administrative records.', 'The unweighted κ test statistic was used to test the agreement between survey responses and WIC administrative data. Substantial to almost perfect agreement was found between the two measures.'] Are wIC infant food package issuance data a valid measure of infant feeding practices?