Objective: To compare knowledge gains and knowledge retention of healthful eating and active living behaviors in elementary school children participating in Educational Theatre Programs (ETP). Methods: The study sample included 47 schools (2,915 third- or fourth-grade students) in 8 Kaiser Permanente regions. Children's knowledge of 4 healthful behaviors was measured using a brief survey before and immediately after performances, followed by a post-delay survey 3 weeks later. Results: Statistically significant increases in knowledge pre/post for individual topics (P less than 0.01). The percentage of children who answered all 4 questions correctly increased from 17% to 63% immediately after ETP performances (P less than 0.01). Knowledge was retained over the short term; the proportion of students who correctly identified recommended healthful eating/active living practices had declined only slightly 3 weeks later. Conclusions and Implications: The ETP significantly improved participating students' knowledge of healthful eating and active living concepts. Theater programs should be considered for inclusion in elementary school health curricula. (Contains 3 tables.)