This study proposes two models for exploring the lexical contents of Part One of the most popular Arabic as a Foreign Language textbook series, Al-Kitaab fii Ta'allum Al-'Arabiyya. Through the lens of a word families framework, this study hypothesizes on the contents and arrangement of the L2 Arabic mental lexicon after completing the textbook. Through counting lexemes, lemmas, and word family members, it is possible to gain insight into the quantity of vocabulary items present within the textbook outside of traditional measures like the triconsonantal root. Through a frequency-based framework, this study analyzes textbook vocabulary items in light of the 5,000 most frequent lemmas in the language from a corpus of 30 million tokens from A Frequency Dictionary of Arabic (Buckwalter and Parkinson: 2011). A comparison between textbook vocabulary and frequency data points to the relationship between the vocabulary studied by AFL learners and the most widely used forms in the language as a whole. While this study gives special consideration to frequency data up to the 3,000 word level, the sheer amount of lexical knowledge necessary for reading Arabic newspapers and novels necessitates integration of frequency-derived data at even the novice level. A lexical and frequency-based approach to AFL instruction and curriculum design may prove helpful in decreasing the decidedly large vocabulary burden (Nation: 1990, cited in Young: 2011) for learners of Arabic as a Foreign Language.