Background: Enjoyment of physical activity is as an important determinant of children's participation in physical activity. Despite this, there is an absence of reliable measures for assessing children's enjoyment of play activities during school lunchtime. The purpose of this study was to develop and assess the reliability of the Lunchtime Enjoyment of Activity and Play (LEAP) Questionnaire. Methods: Questionnaire items were categorized employing a social-ecological framework including intrapersonal (20 items), interpersonal (2 items), and physical environment/policy (17 items) components to identify the broader influences on children's enjoyment. An identical questionnaire was administered on 2 occasions, 10 days apart, to 176 children aged 8-12 years, attending a government elementary school in regional Victoria, Australia. Results: Test-retest reliability confirmed that 35 of 39 LEAP Questionnaire items had at least moderate kappa agreement ranging from 0.44 to 0.78. Although 4 individual kappa values were low, median kappa scores for each aggregated social-ecological component reached at least moderate agreement (0.44-0.60). Conclusions: This study confirms the LEAP Questionnaire to be a reliable, context-specific instrument with sound content, and face validity that employs a social-ecological framework to assess children's enjoyment of school play and lunchtime activities. (Contains 2 tables and 2 figures.)