This study explores the following research question: How do secondary English learners (ELs) and Re-designated fluent English proficient students (RFEPs) use academic words in analytical writing in comparison to native English speakers (NESs)? It highlights previously overlooked differences in academic word use in the writing of students who are in the process of developing English as a new or additional language and NESs who are highly proficient in English. In addition, it explores differences in academic word use between ELs who still require English language support services and RFEPs who do not require these services. The goal of the study is to understand the specific ways various groups of secondary students use academic vocabulary in the Assessment of Literary Analysis, an in-class writing exam, which assesses students' interpretive reading and analytical writing ability that was developed by Olson and Land (2007). The data are drawn from year one of Olson's (2005) University of California, Irvine (UCI)/California Postsecondary Education Commission (CPEC) Accelerating Academic Literacy Project, a collaborative venture between the UCI Writing Project in the Department of Education at UC Irvine, Lynwood Unified School District and Paramount Unified School District. From Olson's (2005) study, student essays were selected for analysis. These included 50 essays from ELs, 50 essays from RFEPs, and 50 essays from NESs. The Vocab Profile (Cobb, 2002), a web-based lexical text analysis tool, first developed as an off-line version, was used to measure the proportions of academic words used in written texts, and text analysis was used to explore word use. There are five important findings: 1) all three student groups used less than 1% of academic words in their writing; 2) NESs used more academic words in their writing than RFEPs and ELs, and RFEPs used more than ELs; 3) NESs used more words, overall, than RFEPs and ELs, and RFEPs used more than ELs; 4) RFEPs made fewer academic word errors, overall, than ELs, and NESs made more academic word errors, overall, than RFEPs; and 5) NESs used academic words more effectively to create cohesion, add vivid detail, and create precision than RFEPs and ELs. Statistical analyses found no significant differences between the three groups of students, although slight differences in academic word use and misuse are notable. This study on academic word use and misuse among secondary students of different English language proficiencies contributes to previous research on academic word use in analytical writing, and addresses previously overlooked linguistic differences between two groups of ELs--RFEPs and ELs. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]