This study aims to describe some of the phonetic variation and characteristics associated with the pronunciation of Northern Ireland English (NIE) in general and the English of rural southwest Tyrone (ERST) in particular. Vowel quality, i.e. the precise sound of the vowels used, expressed in acoustic terms, and vowel quantity, i.e. how long vowels are relative to each other and to surrounding consonants, are of central interest here. ERST vowels may be relatively short or relatively long, depending on factors that are not phonologically relevant in other varieties of English. Vowel shifts from Middle English are only partly carried through, leading to variation according to context and register. Exactly which or a number of possible vowel qualities a speaker chooses to use in a given situation can have sociophonetic significance. Some sounds are clearly stigmatized and can be selectively used or avoided by speakers to achieve desired effects.