The monitoring of must fermentation in a bioreactor, in which the main physico-chemical parameters are tightly controlled, can provide useful analytical information transferable to winemaking on a larger scale. In this experiment, we followed the growth of Saccharomyces cerevisiae during the bioreactor-assisted alcoholic fermentation of a Chasselas must by means of flow cytometry. We used fluorescent dyes and volumetric counting to monitor cell viability and concentration for two weeks. Our study suggests that the use of flow cytometry during bioreactor-assisted alcoholic fermentation provides various types of information—viz., cell viability, number and function—in a timely manner, and that the process can therefore be used effectively to inform experimentation at this scale.