Abstract: Electromagnetic driving mechanism for oscillating displacement pumps (10) is described which comprises a linear motor (21, 22) and a control circuit (51, 52, 53, 54). The control circuit controls the stroke movement of the linear motor (21, 22) in response to the deviation of the actual value of a stroke parameter (stroke distance, stroke speed, stroke acceleration, and pressure of the medium being pumped) from the reference value of this stroke parameter. A preferred embodiment is assembled in such a manner that the pump (10) proper may be easily exchanged and constructed as a discardable unit. Such a pump unit (10) is particularly desirable in connection with blood pumps.