Thermal conductivity of dielectric films can be measured by determining the travelling time of a thermal pulse propagating through the film. In the approach to thermal conductivity measurements described here, the energy of a laser-pulse is deposited into the test sample consisting of a totally absorbing substrate and a thin transparent test layer. As a consequence, a temperature profile builds up at the substrate-film interface. The time delay of the temperature rise at the surface of the test layer is determined by the propagation time of the thermal pulse through the layer, and is directly related to the thermal diffusivity and the thickness of the layer. Measurements were carried out with a preliminary setup and evaluated by calculations on the basis of the finite differences method. Thermal conductivity was determined for single layers of Al2O3, SiO2, and Ta2O5 films. The measurements indicate that the thermal diffusivity is dependent on the film thickness and are essentially smaller than the corresponding bulk values.