Increased attention to large-scale assessments, the growing number of English language learners in schools, and recent inclusionary policies have collectively made assessment accommodations a hotly debated issue, especially regarding the validity of test results for English language learners. Decisions about which accommodations to use, for whom, and under what conditions, are based on limited empirical evidence for their effectiveness and validity. Given the potential consequences of test results, it is important that policymakers and educators understand the empirical base underlying their use. This article reviews test accommodation strategies for English learners, derived from "scientifically based research." The results caution against a one-size-fits-all approach. The more promising approaches include modified English and customized dictionaries, which can be used for all students, not just English language learners. (Contains 3 notes and 1 table.)