Abstract: A piston pump for conveying cryogenic fluids, especially liquid hydrogen, permits reliable transport of relatively large amounts of the fluid at high conveying pressures even with horizontal operation of the pump. The actual pump is inserted in an inner casing pipe (3, 25) of a vacuum housing. The pump is connected by a thread at one end of the housing and sealed against the atmosphere by an O-ring. The cylinder of the piston pump is sealed with respect to the inner casing pipe on the high-pressure side as well as on the low-pressure side by means of synthetic resin gaskets.