AbstractAn electron cyclotron resonance heating (ECRH) system is presently under construction at Commissariat à l'Energie Atomique (CEA) Cadarache for the Tore Supra experiment. The generator is planned to be made of six gyrotrons giving RF waves with a frequency of 118 GHz and a unit power of 400 kW (500 kW) for a pulse length of 210 s (5 s); two of them are already installed: the prototype was first tested on various dummy loads and on plasma and the first series tube is still being tested on a CW load. The results are presented in the following paper.