This book approaches the empirical validation of a popular method of assessing lexical knowledge – the yes/no vocabulary test or lexical decision task – from an interdisciplinary perspective. Each of its chapters sets out a distinct phase of the research along the development of a business English vocabulary test. The book offers a linguistic discussion of business English vocabulary, a psycholinguistic discussion of what aspects of linguistic knowledge and (meta)cognitive processing mechanisms are involved in completing the task, a psychometric-methodological discussion of how these aspects are measured and scored, and an applied discussion of the usefulness of the test. Thus, it is of interest to researchers, students, and professionals from a range of disciplines.