A System working at the Electron Cyclotron Resonance frequency is under construction at CEA Cadarache for heating and current drive experiments in the thermonuclear controlled fusion field of research. This system will be able to couple 3 MW with a 5 s pulse length or 2.4 MW for up to 600 s into the plasma of the Tore Supra Tokamak at the resonant electron cyclotron frequency of 118 GHZ. The main component of this system is the gyrotron TH 1506B developed in a collaborative effort between European research laboratories and Thales Electron Devices. Six gyrotrons of this type will be installed and connected to the Tokamak through six transmission lines made of corrugated waveguides. The RF power will be injected in the plasma by an antenna mainly consisting of several mirrors, either fixed or movable to launch adequately the beams. Two gyrotrons have already been manufactured and tested first on water loads and subsequently on plasma. During tests on dummy load, some limitations in the performance have been observed due to spurious oscillations within the gyrotron itself leading to excessive power deposition on certain components. These results necessitates further studies in order to improve the design of the remaining tubes in such a way that the delivery of the full specification (400 kW, up to 600 s) becomes possible. On plasmas, some experiments were carried out at the end of 2001, with injection of the power under different toroidal and poloidal angles, different polarizations of the electric field and with the RF power modulated up to 25 Hz. A clear increase of the electron temperature has been observed, confirming the deposition radius as predicted by ray tracing calculations. The paper will give a full description of the ECRH system, along with the features of the TH 1506B gyrotron. A presentation of the tests performed on dummy load will be made indicating the analysis of the observed limitations and the possible improvements to be made. The mains results obtained during the experimental campaign of 2001 will also be presented.