Purpose: The goal of this study was to ascertain the effect of changes in stress and speech rate on vowel coarticulation in vowel-consonant-vowel sequences. Method: Data on second formant coarticulatory effects as a function of changing /i/ versus /a/ were collected for five Catalan speakers' productions of vowel-consonant-vowel sequences with the fixed vowels /i/ and /a/ and consonants: the approximant /d/, the alveolopalatal nasal /?/, and /l/, which in the Catalan language differs in darkness degree according to speaker. Results: In agreement with predictions formulated by the degree-of-articulation-constraint model of coarticulation, the size of the vowel coarticulatory effects was inversely related to the degree of articulatory constraint for the consonant, and the direction of those effects was mostly carryover or anticipatory in vowel-consonant-vowel sequences with highly constrained consonants (/?/, dark /l/) and more variable whenever the intervocalic consonant was less constrained (/d/, clear /l/). Stress and speech-rate variations had an effect on overall vowel duration, second formant frequency, and coarticulation size but not on the consonant-specific patterns of degree and direction of vowel coarticulation. Conclusion: These results indicate that prosodically induced coarticulatory changes conform to the basic principles of segmental coarticulatory organization.