OER Knowledge CloudJournal ArticleClinton, VirginiaKhan, ShafiqOpen textbooks have been developed in response to rising commercial textbook costs and copyright constraints. Numerous stud-ies have been conducted to examine open textbooks with varied findings. The purpose of this study is to meta-analyze the findings of studies of postsecondary students comparing learning performance and course withdrawal rates between open and commer-cial textbooks. Based on a systematic search of research findings, there were no differences in learning efficacy between open textbooks and commercial textbooks (k = 22, g = 0.01, p = .87, N = 100,012). However, the withdrawal rate for postsecondary courses with open textbooks was significantly lower than that for commercial textbooks (k = 11, OR (odds ratio) = 0.71, p = .005, N = 78,593). No significant moderators were identified. Limitations and future directions for research, such as a need for more work in K–12 education, outside of North America, and that better examine student characteristics, are discussed.2019EnglishAERA Open531-20United States10.1177/2332858419872212yesopen textbookscourse withdrawalopen educational resourcesmeta-analysis2332858419872212.pdfUnited States, North America