Compound vacuum pump comprises a turbo molecular stage positioned at the inlet end of the pump. It also includes a stator formed from an array of stationary blades and a rotor formed from a further array of blades. A molecular drag stage is positioned at the outlet end of the pump and comprises two discs arranged for rotation within a stator. A flow passageway linking the turbo molecular stage with annular channels is defined between the stator and opposing faces of the discs. The projections extending from the stator are provided for deflecting gas being pumped from the annular channels.