Abstract: A mobile system for electron beam intraoperative radiation therapy uses a race-track microtron placed in a housing playing the role of the vacuum chamber, which is supported by a positioner providing its motion with six degrees of freedom with respect to a patient. The positioner is a part of a mobile mechanical structure which houses an ion pump, a microwave source, waveguide elements, a modulator with a pulse transformer and a cooler. The intraoperative radiation therapy system has a tube-like unit which couples the vacuum chamber with the mobile supporting mechanical structure and provides three functions, namely pumping out of the air from the vacuum chamber, feeding of the race-track microtron accelerating structure with radiofrequency power and rotation of the vacuum chamber with respect to the horizontal axis of the unit.