This part of EN 1159 describes the laser flash method for the determination of thermal diffusivity of ceramic matrix composites with continuous reinforcements (1D, 2D, 3D). The experimental conditions are such that the material behaves in an homogeneous manner for each of its axes of anisotropy and that the heat transfer occurs only by thermal conduction. The method is applicable to materials which are physically and chemically stable during the measurement, and covers the range of temperature between 100 K and 2 800 K.