The sugar transport, fermentative alcohol dehydrogenase (ADH) and protease activities of different industrial strains of Saccharomyces cerevisiae were measured during batch alcoholic fermentation. These strains exhibited different apparent loss of activity of sugar transport, which seemed to be characteristic of each one. A good correlation was found systematically between the integration of sugar transport activity along fermentation and the maximum amount of sugar consumed during fermentation. In all strains sugar transport activity exhibit a lower half-time than fermentative ADH activity. These progressive declines of both sugar uptake and ADH activities of Saccharomyces cerevisiae during batch fermentation seemed to not result from an increase in the protease activity.