During the last few years, systematic investigations of the response of the plasma-facing material to the plasma-wall interaction have been carried out. The goal of this work is to find materials which, on the one hand, withstand the plasma attacks, and, on the other hand, do not contaminate the plasma. The available results allow first systematic conclusions on the status of materials development and on the way that has still to be covered to reach acceptable solutions for this problem area. In this paper, the available test facilities are presented, together with the target values on which the material tests are aiming. The first systematic test results are discussed for non-metallic materials and the conclusions that can be drawn on the status of the already reached position. This is done on the basis of the materials work performed at the Institute for Reactor Materials in cooperation with the Institute for Plasma Physics of the Nuclear Research Center, Jülich.