The heightened importance of foreign languages (L2) in the post 9-11 world demands more L2 listening research as listening is considered the most critical skill for most American military linguists. Some larger studies show that lexical knowledge can positively affect L2 listening (Chang, 2007; Mehrpour & Rahimi, 2010; Staehr, 2009), yet large-scale empirical evidence in non-English L2 is extremely rare. This study explored (1) the relationship between aural lexical knowledge and L2 listening comprehension, both measured by the Online Diagnostic Assessment (ODA), among American learners of the eight diverse languages: Arabic Levantine, Chinese, Korean, Pashto, Persian Farsi, Russian, Spanish, and Urdu, and (2) the regression model to predict the binary outcome of whether students meet the 2+/2+ DLPT goal in listening and reading or not among those learners of the eight languages. This study utilized a considerable amount of pre-existing secondary data of three layers: (1) baseline data to provide a backdrop for 5,023 students included DLPT, GPA, and official course grades, (2) ODA data set consisted of 1,026 listening cases, and (3) 814 cases of Semesters I and II GPAs and listening unit test scores. Correlation analysis showed a strong positive correlation (0.5~0.8) between comprehension and lexicon at the target level for all eight languages. Additionally, in most languages, logistic regression models selected by the Akaike information criterion included Semester 2 GPA and one or two of the four ODA listening-related variables. [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.]