A ccessibility and accommodations in assessments now are seen as critical elements of an appropriately designed and implemented assessment of student achievement. The inclusion of all students in assessment systems designed to measure student knowledge and skills in various content areas has generated considerable and sometimes frenzied activity during the past two decades. This activity has taken place primarily at the state and national levels. With the funding of large consortia of states developing common assessments designed to measure college and career readiness, attention to accessibility and accommodations is being considered as well.The purpose of this chapter is to review what has happened, and what is likely to happen, as accessibility and accommodations research and practice for content assessments are advanced to ensure the appropriate inclusion and validity of assessment results for English learners (ELs) and students with disabilities. A description of accommodations and research specific to access for these two populations is beyond the scope and can be found in other chapters. Although we focus primarily on largescale content assessments used at the state, consortia, and national levels, much of what has happened in these assessments has direct implications for district content assessments and classroom-based assessments (e.g., online embedded tasks, publisher quizzes, teacher-developed quizzes, observational tools, performance tasks, etc.). Thus, we highlight some of those implications as well.Toward this end, we start by defining the many terms that have emerged around the topics of accessibility and accommodations. We address how these concepts have 556076R REXXX10.3102/0091732X14556076Review of Research in EducationThurlow, Kopriva: Advancing Accessibility and Accommodations research-article2014