A hemodialysis machine is described that has an extracorporeal circuit that is primed automatically prior to connection of the patient to the machine. The priming is accomplished by filling the extracorporeal circuit with a priming fluid, such as a saline or dialysate solution or blood. The blood pump and clamps in the arterial and venous lines are operated by a control system in a fashion to create multiple brief pressure pulses in the priming fluid. The pressure pulses shear air bubbles present on the blood side of the dialyzer membrane off the membrane. The blood pump is then operated to clear the bubbles from the dialyzer compartment where they are removed from the priming fluid by conventional bubble trap apparatus.