The behaviour of carbon materials under thermal load in fusion reactors has been simulated by laser-pulse irradiation in a scanning electron microscope (SEM). In this way material damage, such as thermal shock crack formation and propagation, and erosion behaviour, can be studied in situ in the SEM with high lateral resolution. The dependence of damage initiation and propagation on the laser-beam parameters (pulse number, energy, spot size, spot duration and energy density), is of special interest. The damage behaviour is strongly determined by special materials structures. Because of its fibre reinforcement, the investigated CFC composite materials proved to be more stable to erosion and crack formation than homogeneous fine-grained graphites. High-temperature damage may be diminished by the use of carbon materials with creep-resistant components.