In this study, we report on results of a preliminary acoustic–phonetic analysis of the Hidatsa vowel system. We conducted acoustic measurements of Hidatsa vowels in terms of averaged temporal and spectral properties of these phones. Our durational analysis provides strong evidence that Hidatsa has a ten-vowel system with phonemically long and short vowels, in addition to two diphthongs. Our spectral measurements consisted of averages and time-evolution dynamic properties of the first three formants (F1, F2 and F3) at 30 equally spaced time points along the central portion of each vowel. The centers and distributions of the F1 and F2 formants, as well as their time-averaged trajectories, provide strong evidence for separate vowel qualities for both the short and long vowels. These measurements also show that all Hidatsa vowels have some degree of time-dependent spectral change, with the back vowels generally displaying a longer time-evolution track. Lastly, our results also indicate that in Hidatsa mid-short vowels do not appear with the same frequency as the other vowels, and that the short [é] has no unstressed counterpart.