Continuous fermentation using the industrial saccharomyces cerevisiae diploid strain ww was carried out under acidic or high-teinperature conditions to achieve acid-or thermo-toierant mutants. Mutants isolated at PH 2. 5 and 41 °c _---showed improved growth and fermentation ability under acidic and elevated temperature conditions. Haploid strains WW17A1 and WW17A4 obtained from the mutated diploid strain WW17A showed better growth and 4.5-6. 5%higher ethanol yieldaContinuous fermentation using the industrial stïccltaromyces cerevísiae diploid strain ww was carried out under acidic or high-teinperature conditions to achieve acid-or tinermo-toierant mutants. Mutants isolated at PH 2. 5 and 41 °c _---showed improved growth and fertrientation ability under acidic and elevated temperature conditions. Haploid strains WW17A1 and WW17A4 obtained from the mutated diploid strain WW17A showed better growth and 4. 5-6. 5% higher erhanol yields at PH 2. 7 than tlie original strains. Haploid strain WW12T4 obtained from mutated dipoid strain WW12T showed 1. 25-1. 50 times and 2. 8-4. 7 times higher total cell number and cell viability, respectively, than the original strains at 42 · C S : rain AT, which had significantly improved acid-and thermo-tolerance, was developed by mating strain WW17A1 with WW1274. Batch fermentation at 4VC and PH 3. 5 showed that the ethanol concentration and yield achieved during femlentation by strain AT were 55. 4 gjL and 72. 5%, respectively, which were 10 gtt. And 13. 4% higher than that of the original strain WW. The present study demonstrates that continuous cultivation followed by haploidization and mating is a powerful approach for enhancing the tolerance of industrial strains. % higher erhanol yields at PH 2. 7 than tlie original strains. Haploid strain WW12T4 obtained from mutated dipoid strain WW12T showed 1. 25-1. 50 times and 2. 8-4. 7 times higher total cell number and cell viability, respectively, than the original strains at 42 · C S : rain AT, which had significantly improved acid-and thermo-tolerance, was developed by mating strain WW17A1 with WW1274. Batch fermentation at 4VC and PH 3. 5 showed that the ethanol concentration and yield achieved during femlentation by strain AT were 55. 4 gjL and 72. 5%, respectively, which were 10 gtt. And 13. 4% higher than that of the original strain WW. The present study demonstrates that continuous cultivation followed by haploidization and mating is a powerful approach for enhancing the tolerance of industrial strains.