A transient technique for measuring the thermal diffusivity of different solid materials between room temperature and 1000 degrees C is presented. A temperature signal is transferred from a filament to the front surface of the sample and detected with a thermocouple near the front surface. This temperature signal starts a temperature equilibration process in the sample, which is observed at the rear surface of the sample with a difference thermocouple. The transferred heat is an irregular function of the time and is used to calculate the hypothetical equilibration at the rear surface. Hypothetical curves are calculated for given thermal diffusivities with a finite-difference scheme. The thermal diffusivity of the finite-difference scheme is systematically varied to obtain an optimum fit between hypothetical and measured equilibration behavior. The method is applied to various materials, such as quartz and C/C-materials of different orientation, a rock sample, a suevite glass and an yttria-stabilized zirconia ceramic. The different thermal transport mechanisms of the samples (phononic, electronic, advective, radiative) are discussed. Low temperature gradients and small temperature differences in the sample during the experiment allow the measurement of thermal diffusivities near phase transitions and during mineral reactions. The described method is capable of measuring the thermal diffusivities of solid samples between 0.1 and 100 mm 2 /s with an internal precision better than 3% at temperatures up to 1000 degrees C.