The influence of fermentation temperature (from 15 to 35 degrees C) on a mixed strain population was studied. Mitochondrial DNA analysis was used to differentiate Saccharomyces cerevisiae strains and the frequency of each strain during the alcoholic fermentation was determined. The chemical analyses of resulting wines were carried out. The temperature determined how Saccharomyces strains developed and how effectively they fermented. Some strains performed better at high temperatures and others at low temperatures. The maximal population size was similar at all temperatures. At low temperatures, however, it was reached later though it remained constant throughout the alcoholic fermentation. On the other hand, viable cells decreased at high temperatures, especially at 35 degrees C. Obviously, the composition of the wines changed as the temperature of fermentation changed. At low temperatures, alcohol yield was higher. Secondary metabolites to alcoholic fermentation increased as the temperature increased. Glycerol levels were directly affected by temperature.