Various acidic catalysts (zeolitic and amorphous FCC catalysts, mordenite, montmorillonite, and sulfonic ion exchange resin) were tested for the synthesis of acetal from ethanol and acetaldehyde, at 4 and 20 degrees C and atmospheric pressure in batch stirred reactors. All the catalysts were active, but the exchange resin showed a much better performance than the other catalysts, since it quickly reached equilibrium ethanol conversion values. The resin was also tested under different pressures and catalyst to reactants ratios. Clear relationships between the catalyst activity, the amount of acidity and the physical properties of the catalysts were not apparent. A possible reaction mechanism suggests that protonic acid sites are necessary. Water, a reaction product, seems to have an inhibitory effect on the reaction rate.