This study investigated the internal factor structure of the English language development Assessment (ELDA) using confirmatory factor analysis. ELDA is an English language proficiency test developed by a consortium of multiple states and is used to identify and reclassify English language learners in kindergarten to grade 12. Scores on item parcels based on the standards tested from the four domains of reading, writing, listening, and speaking were used for the analyses. Five different factor models were tested: a single factor model, a correlated two-factor model, a correlated four-factor model, a second-order factor model and a bifactor model. The results indicate that the four-factor model, second-order model, and bifactor model fit the data well. The four-factor model hypothesized constructs for reading, writing, listening and speaking. The second-order model hypothesized a second-order English language proficiency factor as well as the four lower-order factors of reading, writing, listening and speaking. The bifactor model hypothesized a general English language proficiency factor as well as the four domain specific factors of reading, writing, listening, and speaking. The Chi-square difference tests indicated that the bifactor model best explains the factor structure of the ELDA. The results from this study are consistent with the findings in the literature about the multifactorial nature of language but differ from the conclusion about the factor structures reported in previous studies. The overall proficiency levels on the ELDA gives more weight to the reading and writing sections of the test than the speaking and listening sections. This study has implications on the rules used for determining proficiency levels and recommends the use of conjunctive scoring where all constructs are weighted equally contrary to current practice. [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.]