REGISTER JOURNAL Vol. 13, No. 1, (2020), pp.123-152 p-ISSN: 1979-8903 ; e-ISSN : 2503-040X Website: http://journalregister.iainsalatiga.ac.id/index.php/register/ 123 Investigating Cultural Dimensions in EFL Textbook by Using Byram Checklist *Soni Ariawan 1 Universitas Islam Negeri Mataram 1 , English Language Education Study Program, Faculty of Education and Teacher Training E-mail : soniariawan@uinmataram.ac.id Corresponding Author* DOI: https://doi.org/10.18326/rgt.v13i1.123-152 Submission Track: Received: 25-03-2020 Final Revision: 23-05-2020 Available online: 01-06-2020 ABSTRACT The present study is a content analysis that aims to investigate cultural dimension in an English textbook prescribed for senior high school in Indonesia which is officially published by the Ministry of Education and Culture in 2017. The data include 11 conversations, 17 reading texts, and 83 visual elements that are analysed qualitatively by employing Byram’s checklist. The findings show that stereotypes and national identity dominate the cultural dimensions with 28.05% and followed by social interaction and socialisation and life cycle with 15.9%. The occurrence of national geography