Because most–if not all–intensive English programs (IEP) assign students to specific levels based on a placement test that does not involve any form of explicit vocabulary testing, some degree of variation in lexical knowledge of students within an individual class should not be surprising. However, very little research has ever quantified this variation. The current study fills the gap in this important area of TESOL research by investigating vocabulary variation among intermediate-level students at one IEP. Participants (N=79) were split into two main proficiency groups, high intermediate (N=28) and low intermediate (N=51). The 2K, 3K, and 5K levels from the Vocabulary Levels Test (VLT) were used as a vocabulary measure. In this study, VLT scores were analyzed by proficiency level and by students' original individual classes (N=7). The results revealed considerable vocabulary variation. In some instances, vocabulary size varied by 900 word families per student. First language influence was also investigated by comparing the largest two language groups in the sample, Arabic (N= 28) and Spanish (N=12). Spanish-speaking students significantly outperformed the Arabic speaking students in all vocabulary measures (except for the 2K level). The study, therefore, raises questions about the approaches used in teaching a class that has both Spanish and Arabic speakers. Implications and suggestions for further studies are discussed.