This is the first book-length study that, from a typological perspective, deals with the latest phonological changes which have affected the spoken standards of the three major West Germanic languages and offers a uniform theoretical analysis of the phenomena. It is primarily intended for professional linguists, but is also geared toward language instructors and students who want to acquaint themselves with these mainly vocalic developments in the pronunciation norms. The study is empirically grounded in personal auditory observations, which in many instances, however, have been verified elsewhere by instrumental acoustic evidence. For each of the three languages, including the American and British English standards, two vowel systems are described and explained: a conventional and slightly dated system, certain features of which younger speakers are inclined to consider somewhat stilted or outmoded, and a more modern and progressive system that incorporates substantive changes and seems to be favored by younger speakers. While a hypothesis is briefly put forward on the common sociopolitical causes of the recent changes, the main phonological finding relates to the role of vowel quantity. In the progressive systems of the three languages, segmental vowel length proves to be a secondary phonological parameter correlating with a specific phonotactic property of the sound.