Vocabulary is considered the building block of language. Without it, communication breaks down. This degree project investigates the vocabulary types, progression, lexical coverage andacademic words in EFL upper secondary textbooks in Sweden. This was done by a corpus-based approach using corpus tools such as Range and AntWord Profiler. The entire corpus contained six textbooks from two different series: Solid Gold and Viewpoints. These textbooks are utilised in English 5, 6, and 7 upper secondary courses. The analysis focused on Nation's word types and Coxhead’s Academic World List, including progression and coverage. The results revealed that high-frequency vocabulary is maintained throughout the series, while mid-frequency vocabulary considerably increases as the textbook levels progress. Results also show that around 3,000 word families are needed for 95% lexical coverage and 6,000 word families for 98% lexical coverage. Each textbook increases around 1,000 word families per level, but is less proportional in relation to the word count. The highest increase of word families is 32% and the lowest of 17%. Furthermore, the study found that the AWL covers 7% of the vocabulary, and 80% of the AWL items are used. Pedagogical recommendations from this study include establishing a vocabulary input threshold per level to ensure consistent progression. Additionally, academic written genres such as Introduction-Method-Results-Discussion (IMRaD) structures can be included in the textbooks in addition to the existing literary genres to help prepare Swedish L2 learners to cope with university academic texts.