A method and apparatus for the air-free filling of the blood side of a hemodialysis apparatus with a physiological electrolyte solution and for the venting of the blood side of a hemodialysis apparatus during operation includes using a chamber in a blood-removing line system. The blood-removing line system, including the chamber arranged therein, is filled with a physiological electrolyte solution, with a valve arranged above the chamber and connected thereto being opened to fill the chamber completely with the physiological electrolyte solution until it comes into contact with a hydrophobic filter arranged above the valve.
