Continuous production of ethanol by fermentation with immobilized yeasts gives a betler yield and capacity and can be better controlled than conventional processes with batch reactors and a suspended biomass. This paper ( the first of three) examines the operative conditions for immobilizing Saccharomyces Cereuisiae on beech wood cubes. After preliminary evaluation of the non-influence of mass transfer phenomena and the extent of alcoholic inhibition, an experimental investigation of the kinetics for a metabolic reaction in a continuous recycle reactor was carried out. The kinetic equation was found to be a Michaelis-Menten type with uncompetitive inhibition by substrate, and linear inhibition by product.