Using various fermentation media, ethyl alcohol production in a packed bed reactor with S. cerevisiae, immobilized in calcium alginate gel, was investigated. For the rich medium, productivity changed between 17 and 21 g /1. hr, during a period of 52 days. When a poor me- dium was used, during a period of 10 days productivity decreased to 72 % of the initial value and, when molasses solution was used, the productivity decreased to 33 % of the initial value. The productivity of the immobilized system turned out to be 7 to 40 times of the free system, depending on the residence time.