"Modals and Quasi-modals in English" reports the findings of a corpus-based study of the modals and a set of semantically-related 'quasi-modals' in English. The study is the largest and most comprehensive to date in this area, and is informed by recent developments in the study of modality, including grammaticalization and recent diachronic change. The selection of the parallel corpora used, representing British, American and Australian English, was designed to facilitate the exploration of both regional and stylistic variation.