["TESOL Quarterly, EarlyView. ", "\nThe purpose of this paper is to explain case study design within the context of applied linguistics and language education research and explore its use in the TESOL Quarterly. It will focus on the history and key conceptual underpinnings of case study design, highlighting the principles that guide its use in research. The paper will also examine the application of this method in TESOL Quarterly research, providing two specific examples to demonstrate in more detail how case studies have been utilized. Additionally, it will offer guidelines for conducting rigorous case study research, outlining best practices to establish reliability and validity. The paper will conclude with suggestions for future research tasks using the case study method, along with an annotated list of recommended readings to further explore the topic.\n"]