Purpose/Objectives: The National School Lunch Program is well situated to address the vulnerability of lower income children at increased risk for both under and overnutrition. Evidence suggests, however, that a significant amount of food served in the program goes uneaten. One way to monitor this problem is through children's self-reported plate waste (PW), but no validated measure exists. Therefore, the purpose of this study was to develop and validate a children's self-report PW questionnaire. Methods: Lunch trays were collected from 54 sixth grade students after lunch. Remaining foods were weighed to determine the percent wasted. The same children completed a PW questionnaire later in the day. To assess validity, students' self reported PW was compared to the weighed quantities. The questionnaire also asked about a series of 15 potential reasons for PW. Reliability of these items was analyzed to assess internal consistency. Twenty-four participants completed the procedures a second time so that test retest reliability also could be determined. Results: Significant correlations were found between weighed and self-reported PW (p<0.05), indicating criterion validity. Test-retest reliability on eight of the 15 PW reasons was significant (p<0.1); an additional four were invariant for at least one of the two time points. The series of items was also internally consistent (Cronbach's alpha = 0.71). Further research is needed to evaluate the instrument across a wider variety of school settings and lunch menus. Applications to Child Nutrition Professionals: Child nutrition professionals may use this valid and reliable self-report measure of children's PW to monitor menu performance in federal child nutrition programs. This instrument may be used to assess changes made to the meals served, which can assist in reaching Healthy People 2010 goals for school nutrition.