The most salient difficulty in assessing English language learner (ELL) students who exhibit academic difficulties is identifying whether the problem is one of English proficiency or of a learning disability. In many cases, the symptoms are shared and difficult to disentangle, but obtaining a comprehensive picture of the child is vital for disability eligibility. The response to intervention (RTI) model provides an additional source of information during the special education referral process, using data driven curriculum-based assessment (CBA) in conjunction with scientifically based instruction. All school professionals addressing the needs of the children who are having academic difficulties will be involved in more meaningful ways during progress monitoring and evaluation of eligibility for special education. This article discusses the prereferral and referral assessment and individualized education program (IEP) development for ELLs within an RTI model, providing a framework for integrating the results from the bilingual English as a second language (ESL) specialist, the classroom teachers, and the multidisciplinary team (MDT). The authors suggest questions and approaches to help guide the team in addressing ESL instructional recommendations for a student's English language proficiency and academic difficulties in the general education classroom and in integrating formal assessments with information on progress monitoring and ESL services when making IEP recommendations. (Contains 2 figures and 3 tables.)