The effect of acetic acid on the growth and the fermentative activity of S. cerevisiae was analysed comparatively with the pH. This study showed that the pH does not affect these two activities. On the contrary, the acetic acid has an inhibition effect. This effect was modelised by the relation of Levenspiel. Finally, it was shown that the quantities of acetic acid produced by Brettanomyces were not sufficient to explain the inhibition of Saccharomyces.