A method for the filling and flushing of a blood tube set including a pump segment for a blood pump, an arterial line connected to an inlet of a dialyser, a venous line connected to an outlet of a dialyser, a substituate line connected to a substituate port and having a pump segment for a substituate pump, and a three-way connector connected to the arterial line, the venous line and a rinse port. The method includes the steps of opening the rinse port, filling and simultaneously flushing the arterial and venous lines with the substituate supplied from the substituate line via the substituate pump, while substituate is drained off via the rinse port, closing the rinse port, and circulating the substituate in the circuit of arterial line, dialyser and venous line by the blood pump.
