Planning language and literacy instruction and supplemental intervention for English Learners (ELs) in bilingual education programs begins by assessing their current performance, strengths, and needs. However, current functioning must be interpreted in relation to past performance and the nature and quality of instruction students have received over time. This article presents guidelines for assessing ELs and recommends the Language and Literacy Assessment Record for English Learners (LLAREL) as a holistic, retrospective framework for documenting students' educational histories, native language and English development, and academic achievement in both languages, longitudinally. Suggestions for interpreting LLAREL data are offered in the context of (a) planning core instruction, (b) identifying students experiencing learning difficulties, (c) designing supplemental interventions, and (d) making special education referral decisions.