Abstract: A lubrication system comprising a first pump (2) to deliver lubricating oil from a reservoir (1) to equipment to be lubricated (9), a second pump (11) to return lubricating oil from the equipment (9) to the reservoir (1), and characterised in that both pumps (2, 11) are mounted on a common drive shaft (19) and each comprises a regenerative type pump with the second pump (11) having an air bleed (40) connected to the reservoir (1) from an inner region of the pump impeller (21) in which air accumulates. The first and second pumps (2, 11) may comprise separate impellers (20, 21) or a common impeller (60 or 74). The second pump (11) may comprise two or more guide channels (34, 34') on the same or opposite sides of the impeller, each associated with a series of cells (32) and respective pump inlet and outlet ports (36, 36'; 38, 38') and an air bleed (40, 40') so as to function as a separate scavenge pump to return lubricating oil to the reservoir (1).