More than 5 million English language learners (ELLs) attend school in the United States (Ballantyne, Sanderman, & Levy, 2008). This population has increased by approximately 57 percent during the last decade, drawing sharp attention to the individual and instructional needs of students who are nonnative speakers of English (Ballantyne et al., 2008). With the rising number of ELLs in American classrooms, general "mainstream" teachers will undoubtedly teach a student who is not proficient in English and therefore unable to access the academic curriculum. These mainstream teachers are expected to teach academic content and raise student achievement while simultaneously developing ELL students' facility in and command of the English language. Emerging research indicates that mainstream teachers are ill equipped to effectively teach ELL students and have little access to preservice and inservice education focused on what to teach and how to teach this underserved population (Ballantyne et al., 2008; Hollins & Guzman, 2005). Coupled with these expectations are the challenges in making sense of the highly politicized debates over English-only and bilingual instruction. For these reasons, preparing effective teachers for this complex classroom and policy environment is critical and the role of teacher education programs is paramount. This Issue Paper presents a review of the policy environment for ELL instruction and the preparation of mainstream teachers to address the needs of ELL students. It also describes the key features of effective instructional practices for ensuring ELL students' learning of academic content supported by empirical evidence. Finally, the paper presents the Innovation Configuration for Preparing Mainstream Teachers of ELL Students, a tool for evaluating mainstream teacher preparation programs and inservice professional development. Appendix includes: Innovation Configuration for Preparing Mainstream Teachers of ELL Students.