α-Acetolactate decarboxylase isolated from Enterobacter aerogenes strain 1033 has been applied for maturation of beer. Addition of the enzyme to freshly fermented beer effected removal of α-acetolactate and α-aceto-α-hydroxybutyrate in 24 hours at 10 °C to a level below the taste treshold of the corresponding volatile diketones, diacetyl and 2,3-pentanedione, without affecting other important properties of the beer. By comparison of organoleptic properties, the beer matured in the presence of α-acetolactate decarboxylase was judged to be of an equally satisfactory quality when compared with conventionally prepared beer. The evidence suggest that apart from removal of diacetyl, 2,3-pentanedione and the precursors of these compounds from fermented beer no other important events related to flavour development occur during maturation of the type of beer studied. Consequently, it is concluded, that application of enzymes may allow flavour maturation of beer to be carried out in less than 24 hours.