Abstract: The invention provides apparatus suitable for use in continuous transfer of workpieces through a region of reduced pressure in which some operation is to be performed on each workpiece in turn, being particularly, but not exclusively, suitable for electron beam welding. The apparatus comprises a sealed chamber, to constitute the region of reduced pressure, and a passageway extending therethrough, with means defining a series of compartments for containing individual workpieces, the compartments being movable in succession along the passageway and through an operating station in the sealed chamber where the interior of each compartment in turn is exposed to the interior of the sealed chamber for the performance of an operation on a workpiece carried in the compartment.