A method and apparatus for filling bottles or similar containers, whereby the containers are rinsed and pre-pressurized with an inert gas in a preliminary pressurizing phase that precedes the filling phase. For the rinsing as well as the at least partial pre-pressurization, the return gas from a return gas channel is utilized. To keep the return gas as free from bacteria as possible, the containers are treated with a sterilization medium in a preliminary treatment phase that precedes the preliminary pressurizing phase. Furthermore, air and sterilization medium that are displaced in the sterilization phase and in the preliminary pressurizing phase are withdrawn to the atmosphere or to a channel that is separate from the return gas channel.