This article presents a critical review of the Texas English Language Proficiency Assessment System (TELPAS), a large scale standardized English language proficiency (ELP) assessment developed by the Texas Education Agency (TEA) and administered since 2004. TELPAS is used as an annual summative assessment for all English Learners (ELs) in grades K-12 and is administrated annually to approximately one million ELs in Texas. It is a high-stakes assessment impacting students, campuses and districts in multiple ways including EL reclassification decisions, campus and district accountability, language program evaluation, and instructional/assessment accommodation decisions. TELPAS has not been critically reviewed previously and little research has investigated its impact on the large EL population in Texas or other stakeholders. TEA has recently made many structural changes to TELPAS making this an ideal time to review the assessment. The current review showed TELPAS to be a sound instrument but there is room for improvement. Recommendations include increased frequency of released tests to allow for external reviews of the assessment, steps to take to allow for a more rigorous inter-rater reliability study, an in-depth reliability study of the new machine scoring of listening and speaking, and a robust consequential validity study.