The glycerol 3-phosphate dehydrogenase (GPDH; EC 1.1.1.8) activity of cells subjected to heat shock treatment increased 1.15- to 1.25-fold over that of cells not heat shocked. The increased GPDH activity induced by heat shock treatment extended over several generations, but gradually decreased through subcultures, The effect of heat shock treatment during the pre culture stage on glycerol production in the main culture was investigated with the shochu yeast BAW-6 (Saccharomyces cerevisiae). Heat shock at 45 and 50 degrees C was effective for glycerol production, but there was no influence at 35 degrees C. The timing of the heat shock treatment did not influence glycerol production. Enhancement of glycerol production induced by heat shock was also observed in the sake yeast K-7, wine yeast W-3, beer yeast IFO1167, and whisky yeast IFO2363. Shochu was produced by using heat shocked BAW-6. The glycerol concentration in the mash was increased by heat shock treatment, thereby improving the aroma and taste of shochu produced from this mash. In addition to shochu, glycerol is a key factor influencing the taste of other brewed brewages such as sake or wine. The results suggest that the heat shock treatment during pre culture may be an effective and simple method for improving the quality of shochu, sake, and wine.