This study analyzes ten beginning-level, Spanish-language graded readers in an attempt to answer the question of how much vocabulary do students need to know before being able to successfully participate in an extensive reading program. The study also analyzes the vocabulary taught in a beginning-level Spanish textbook to determine how well this vocabulary reflects the most common words in Spanish according to a frequency dictionary. It was found that a lexicon of 5,000 words was needed to obtain a sufficient level of comprehension in order for extensive reading to occur and that the textbook examined in this study did not present vocabulary that was extremely reflective of the most common words in the Spanish language.