https://doi.org/10.1177/1362168818776671 Language Teaching Research 1–26 © The Author(s) 2018 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1362168818776671 journals.sagepub.com/home/ltr LANGUAGE TEACHING RESEARCH Thirty-five years of ISLA on form-focused instruction: A meta-analysis Eun Young Kang Lehman College, City University of New York, USA Sarah Sok University of California, Irvine, USA ZhaoHong Han Teachers College, Columbia University, USA Abstract This meta-analysis offers a snapshot of thirty-five years (1980–2015) of research on instructed second language acquisition (ISLA). Fifty-four empirical studies involving a total of 5,051 second language learners – sampled from six applied linguistics journals, Applied Linguistics, Language Learning, Language Teaching Research, The Modern Language Journal, Studies in Second Language Acquisition, and TESOL Quarterly – were aggregated for the effects of second language (L2) instruction, yielding an overall large effect size, g = 1.06, 95 % CI = 0.84-1.29. Data were further analysed to identify factors that can modulate the efficacy of instruction. While a minor difference was detected between explicit and implicit instruction, statistically significant effects were found for modes of outcome measures, learners’ onset L2 proficiency, research settings, and intensity of instruction. Keywords explicit instruction, factors influencing efficacy of instruction, implicit instruction, L2 instructional efficacy, meta-analysis Corresponding author: Eun Young Kang, Lehman College, City University of New York, 250 Bedford Park Boulevard West, New York, NY 10468, USA. Email: eunyoung.kang@lehman.cuny.edu 776671LTR 0 0 10.1177/1362168818776671Language Teaching ResearchKang et al. research-article 2018 Article