Abstract: A centrifuge rotor for use in the continuous separation of a liquid into fractions has a recess for receiving a flow-through separation container. The recess has interrupted annular shape with inclined side-walls. The inclination of the sidewalls and the cross-sectional area of the recess increase continuously in the circumferential direction from one end of the recess to the other. A collapsible flow-through separation container having flexible inlet and outlet tubes is adapted to fit within the rotor recess. Its cross-sectional area increases continuously from the inlet end to the outlet end.