Vowel Harmony (VH) in French, as described by Grammont (1933, also see Fouché, 1956; Carton, 1974) has been investigated experimentally by Nguyen & Fagyal (2008). Acoustic analyses of the formant frequencies of vowels produced in [...]V1 CV2 [...] sequences showed that french mid-vowels ([e] ∼ [E], [o] ∼ [O], [ø] ∼ [œ]) tend to exhibit a more peripheral position in the acoustic vowel space when followed by a non-low vowel compared to a mid-low or low vowel: when V2 is low (as in /eta/), V1 tends to be lower than when it is followed by a non-low vowel (as in /ete/). This is apparent in acoustic measurements of both F1 and F2 formant frequencies and the statistical analyses that were performed by the authors are overall significant. Though these data are in accordance with classical views on vowel harmony in French, Nguyen & Fagyal (2008)'s results were based on measurements taken from the acoustic midpoint of V1 vowels. It is usually acknowledged that this temporal midpoint may provide an adequate location for measuring stable patterns of formant frequencies but there are alternative approaches to defining speech targets. One of them states that a better approach to locating the temporal moment where the speaker reaches the vowel static target is to identify the point where F1 reaches its maximum, which would correspond to the time when the vocal tract is maximally open (Lindblom & Sundberg, 1971). According to this proposal, if the time when F1 reaches a maximum precedes the temporal midpoint of the vowel, it would appear that the static vowel target has been reached before the temporal position at which the acoustic measurement has been taken (cf. Fig. 1 for an illustration). Of course, the relationship between maximal F1 position and midpoint may vary. Nevertheless, it is crucial to investigate this issue as, in cases where F1 max would precede the vowel midpoint, evidence of a vowel harmony influence may appear to be the consequence of the formant movement trajectory between two unmodified targets. In order to adress this issue, an experiment was designed to investigate VH phenomena in French at different temporal positions in the supposedly harmonised vowel in order to provide data on the temporal course of formant trajectories when V2 is either a low or a non-low vowel. Four French speakers participated in this experiment. Statistical analyses performed on the first three formants at 3 temporal positions within the first vowel partly confirm Nguyen & Fagyal (2008)'s conclusions. Issues relating to the time course of this phenomenon along the duration of the vowel are discussed according to theoretical approaches to static vs. dynamic vowel targets, calling for additional analyses and experiments.