A method for priming a blood tubing set having a venous line and an arterial line whose connections at the patient side are in communication with two separate inlets of a chamber of, in particular, a bag and whose connections at the machine side are in communication with a dialyzer. The method includes the steps of parallel filling of both the venous and the arterial lines via a feed line so that priming liquid flows through both inlets into the chamber； and circulation of the priming liquid in the circuit of the lines, the dialyzer and the chamber via a pump so that one of the inlets of the chamber acts as an inlet and the other as an outlet.
