Graphites suitable for highly loaded parts of plasma machines have been studied with respect to their heat shock resistances. Seven different grades of fine-grain graphites and three carbon fibre composite (CFC) materials were exposed to a 10kW CO2 laser beam for up to 1.1sec. Surface temperatures up to 2250oC were achieved. The concomittant erosion was determined by mass balance and compared with theoretical loss rates calculated from vapour pressure curves. Measurable erosion sets in at 1800oC and depends strongly on the density of the material (for the isostatically pressed graphites) and on the direction of the fibres with respect to the heated face (for the CFCs). The stresses across the test samples were calculated versus time. Maximum compressive stress of 25MPa is reached on the heated face ca. 0.5s after the start of the laser pulse. Maximum tensile stress is only 40% of compression and occurs after 0.7s near the mid plane of the samples.