Ample studies on content-based instruction (CBI) provide strong evidence as to the effectiveness of this methodology in developing language and content knowledge in students; however, there is much less information as to why this methodology is so effective. Building on the results of a previous study, this paper discusses the findings of a qualitative study to see how CBIsupports language development. The data collected through student interviews and learning journals revealed that the exposure to authentic material that was meaningful, interesting, and relevant to students’ present and future needs, activation of prior knowledge, and the specific methodology used in class were the most important factors which supported language and content development.