Abstract: A vacuum pumping system includes an oil-lubricated rotary vacuum pump, an electric motor driving the pump and a gas ballast arrangement supplying the pump with gas and fluidically coupled with the motor for sucking oil, leaked from the pump into the motor, back into the pump. The fluidic coupling is achieved by means of a leaked oil recovery unit that is housed in a region of an internal chamber of the motor where ballast gas and leaked oil are present and that establishes communication between the region of the internal chamber of the motor and the pumping chamber.