This paper presents an analysis of how the variables of word stress, intonational phrase stress, and the position of the vowel sequence within the phrase affect the production of vowel sequences across word boundaries, generating some external sandhi phenomena. Based on semi-spontaneous data from Brazilian Portuguese speakers, the study suggests that the stress pattern of a word can influence the occurrence of sandhi phenomena or the maintenance of hiatus. However, this also depends on whether the sequence carries the main stress of the intonational phrase, as in "no próximo ano," and if it is located at the rightmost phrase boundary, as in "isso que é." It is observed that the probability of a sandhi phenomenon occurring is higher in contexts where at least the first vowel is unstressed, when neither of the vowels receives the main stress of the intonational phrase, and when they are not at the phrase boundary.