So as to offer greater design freedom for the upstream nozzles since the resistance upon exit of the jet flow into ambient pressure is encountered less abruptly, the invention provides al. multi-stage ejector for generating a vacuum from a source of compressed air by passing said compressed air through a series of nozzles, accelerating said compressed air, and entraining air so as to form a jet flow in two or more stages including at least a drive stage and a second stage and generating a vacuum across each stage before ejecting said jet flow through an outlet of the ejector, wherein said ejector outlet is formed as a nozzle extending to the outlet end of the ejector and arranged to receive the jet flow from the final stage of the ejector, and wherein said ejector outlet nozzle includes a diverging section extending at an angle of divergence to the direction of airflow, said diverging section terminating in a stepwise expansion in the cross-sectional flow area, as viewed in a direction perpendicular to the direction of airflow through the ejector outlet nozzle.