The research effort reported in this document addresses the important national need for determining the validity of large-scale content assessments in English with students who are in the process of acquiring English as a second language. Often these students have been excluded from such assessments, but there have been recent, growing efforts to include them. There is, however, considerable variability nationwide in the inclusion process. The focus of this report is on second language students--English language learners (ELLs)--who have been included in large-scale content assessments regardless of their language ability. Within the context of assuring equal educational access for all students, technical issues around validity are being examined from three perspectives. This report is organized into the following chapters: (1) Examining ELL and Non-ELL Student Performance Differences and Their Relationship to Background Factors: Continued Analyses of Extant Data (Jamal Abedi, Seth Leon, and James Mirocha); (2) Students' Concurrent Performance on Tests of English Language Proficiency and Academic Achievement (Frances A. Butler and Martha Castellon-Wellington); (3) Language Analysis of Standardized Achievement Tests: Considerations in the Assessment of English Language Learners (Alison L. Bailey); and (4) General Discussion and Recommendations (Alison L. Bailey, Frances A. Butler, and Jamal Abedi). (Individual chapters contain references.)