Hiatus resolution, also explained by vowel sequence realization, occurs when a vowel sequence that occupies two syllables in normative speech is reduced to a monosyllabic sequence. In this study, vowel sequence realization was examined by measuring the duration of word-boundary vowel sequences in the speech of Spanish speakers from Cali and Barranquilla, Colombia. Four variables (speaker gender, regional variety, speaking rate, and two-word string frequency) were analyzed to determine their effects on the duration of the unstressed vowel sequences , , , and .