The study deals with the formant movements associated with transitions, glides, and diphthongs in spoken American English. The transitional characteristics associated with all initial and final consonant phonemes were studied in a large sample of utterances. The rate of change of the transition from a consonant hub to the steady state vowel formant position and conversely was investigated for vowels which are commonly considered monophthongs. It is assumed that such changes are cues for the perception of the consonants rather than linguistically significant components of the vocalic nucleus. The rate of change associated with syllable nuclei commonly perceived as diphthongs, [ɑɪ], [ɔɪ], [ɑᴜ] was investigated and compared with the changes due to consonant transitions in monophthongs. Criteria are suggested by which the formant movements due to transitions may be distinguished from movements that have linguistic signalling value within the syllable nucleus.