The influence of vowel duration and vowel formant track shape on vowel recognition were tested with a listening experiment. Listeners heard synthetic vowel stimuli in isolation. The duration of the stimuli varied between 6ms and 150ms. Formant tracks were either constant or were shaped according to a parabolic function. The excursion size of the formant tracks (i. e. maximum - minimum) varied between 0 and 375 Hz. Except for long-short vowel oppositions, the responses of the listeners showed no influence of stimulus duration. The effects of formant track shape on vowel identification can best be explained by assuming perceptual undershoot (i. e. averaging over formant tracks). Keywords: vowel perception, duration, formant tracks