The scripts of 318 movies were analyzed in this study to determine the vocabulary size necessary to understand 95% and 98% of the words in movies. The movies consisted of 2,841,887 running words and had a total running time of 601 hours and 33 minutes. The movies were classified as either American or British, and then put into the following genres: action, animation, comedy, suspense/crime, drama, horror, romance, science fiction, war, western, and classic. The results showed that knowledge of the most frequent 3,000 word families plus proper nouns and marginal words provided 95.76% coverage, and knowledge of the most frequent 6,000 word families plus proper nouns and marginal words provided 98.15% coverage of movies. Both American and British movies reached 95% coverage at the 3,000 word level. However, American movies reached 98% coverage at the 6,000 word level while British movies reached 98% coverage at the 7,000 word level. The vocabulary size necessary to reach 95% coverage of the different genres ranged from 3,000 to 4,000 word families plus proper nouns and marginal words, and 5,000 to 10,000 word families plus proper nouns and marginal words to reach 98% coverage. The implications for teaching and learning with movies are discussed in detail.