Abstract: A method and apparatus for aseptically filling containers with product, such as the bags (B) of bag-in-box containers, wherein the aseptic filling chamber (9 or 40) with a filling head or nozzle (5 or 43) therein is provided with fluid inlet and outlet lines (2,4,6,8,19,21,39 or 57,59,63) to create desired positive or negative atmospheric conditions within the chamber, so that a positive pressure can be maintained within the chamber when change over, at an aperture in the chamber, of a bag to be filled occurs, and so that after filling, a negative pressure (through line 15 or 63) can be generated to evacuate the chamber and hence remove any headspace gas from the top of the filled container prior to it being capped.