Several strains of Saccharomyces sp. and commercial Baker's yeast were immobilized by adhesion onto chrysotile, a fibrous magnesium silicate (Mg6Si4O10 (OH)(8)). The activity of the cells is higher when immobilized, mainly for fermentation of 30 to 50% w/v glucose solutions. In the medium containing 30% w/v glucose, the initial fermentation rate increased 1.2-2.5 times. Yields were in the range of 80.4 to 97.3% for the immobilized cells and 72.7 to 84.5% for the free cells. A packed bed reactor for continuous fermentation was set up using one of the tested strains immobilized onto chrysotile. An average productivity of 20 to 25 g.l(-1).h(-1) was obtained in the first 20 d, and an average of 16 g.l(-1).h(-1) was obtained after 50 d of operation.