Pasteurization is the most common processing method for microbial and enzyme inactivation to preserve foods. With this method, foods are exposed to high temperatures and there are disadvantages for many products: thermal treatments cause modifications of sensory attributes (for instance: flavour, colour, nutritional qualities). Now, another method can replace pasteurization: microbial inactivation by ultrasounds. It is a new alternative technology of food processing also called sonication, and it can be used coupled with pressure and/or heat. These techniques inactivate microorganisms in foods. They are effective and energy efficient to kill them, making the techniques promising for the food industry. In this chapter, the method of microbial inactivation by ultrasounds was explained, after that the applications in food industry for instance in milk, orange juice, wastewater, and whole liquid eggs were well-defined, and finally, the advantages, disadvantages, and the limitations of this method were examined.