This accounts for the effect of intrinsic segmental characteristics on the duration of Brazilian Portuguese oral vowels, compared to durational changes that can be attributed to macro-prosodic features, such as stress location, sentence modality, and syntactic structure. A multispeakers corpus containing logatomes with systematic variations of vowel quality (seven vowels) embedded in sentences with controlled characteristics was recorded. A semi-automatic procedure allowed to segment and measure the duration of 3036 vowels; their duration was fitted to a series of factors, representing the controlled micro-and macro-prosodic characteristics. This modeling process showed the importance of micro-prosodic changes mainly in the case of stressed vowels (explained by jaw aperture and tongue posteriorization), which decreases with the vocalic reduction on prestress and post-stress positions, depending on macro-prosodic factors. The main macro-prosodic effects are linked to stress, the syllable position, final lengthening, and modality.