Abstract: The invention relates to a sealed, sterile system for filtering fluids, in particular whole blood. The system comprises a first collapsible container for receiving the fluid to be filtered and a second collapsible container for receiving the filtered fluid, both containers interconnected by a fluid line, in which a filter and a third container, for deaeration, are located. The first collapsible container contains a predetermined quantity of air, which is sufficient to ensure that no blood remains in the filter and the adjacent tube line sections when the whole blood is transferred from the first container into the second container. The air that is present in the second container, after the whole blood has been filtered, is transferred to the deaeration container.