Abstract: Disclosed is a modification of production of alcoholic beverages such as beer or wine by subjecting to fermentation by means of a faculative anaerobic microorganism such as a yeast a substrate liquor to the microorganism, which modification comprises conducting at least a part of the fermentation under such an anaerobic condition that the content of the dissolved oxygen in the substrate liquor is held at a restricted level thereby to reduce the content of diacetyls which imparts a disagreeable odor to the alcoholic beverages produced. The anaerobic fermentation makes it possible to use a yeast in high concentration without entailing the increase in the quantity of the diacetyls. Typically, the fermentation is conducted in two zones; one zone being conducted under the conditions that the yeast is proliferating while the other under the conditions that the yeast is not proliferating.