Microorganisms influence on production and final chemical composition of wine, but yeasts are most important due to their implementation in alcoholic fermentation, during which high concentrations of sugars in the must are degradated to ethanol. At the beginning of alcohol fermentation intense growth of yeasts is desirable, while the indigenous yeasts and bacteria grow niminally. If yeasts growth is delayed, various types of lactic or acetic acid bacteria grew, inhibiting the growth of yeasts, which leads to sluggish or slow fermentation. Changes in the environment (production of CO2, low pH, the temperature of fermentation and the use of SO2) are responsible for differences in the microbial ecology of the entire process of wine production. It is obvious that the growth of microorganisms in wine-making process depends on various parameters such as microbial interactions, the composition of the media and oenological practices. It is therefore necessary to take care about the health of the grapes, to control breeding and processing of grapes, as well as control the whole process of fermentation, also the stabilization and maturation of wine. And finally, good hygiene practice in wineries is essential.