The vowel phonemes of English conventionally subdivide into ‘pure’ vowels and diphthongs, and diphthongs are a well recognised component of the system. Triphthongs are a different story. The very word ‘triphthong’ sounds faintly preposterous, as if somebody has dared a coinage with ‘diphthong’ and wants to have some further fun. Without wishing to prejudge the question of the actual existence of triphthongs, I shall use the word to refer to a sequence of three vocalic elements that may be interpreted as a single unit and, as a phoneme, has a contrastive function.