Upper Necaxa Totonac is a Totonacan language spoken in the Necaxa River valley in the Sierra Norte of Puebla State, Mexico. While the Totonacan languages historically have three phonemic vowel qualities, the Upper Necaxa system consists of five vowels that contrast length and laryngealization. With acoustic data from six native speakers from the Totonacan communities of Patla and Chicontla, we explore the phonetic properties of vowels with respect to the first and second formant frequencies, quantity (duration), vowel phonation (modal vs. laryngeal), and stress. The data indicate that long, short, modal and laryngeal vowels occupy a similar formant space and that duration is the primary phonetic correlate of phonemic vowel length. A shift in vowel quality and an increase in duration and pitch were shown to be the acoustic characteristics of stress. The study provides a first acoustic analysis of vowels in Upper Necaxa, and contributes to typological descriptions of the properties of vowels connected with quality, quantity, stress, and phonation.