Theoretical bases of the author's method destined, in a perspective, for isotropic material thermal diffusivity in situ measurements are presented in the work. The method employs the properties of general solution of the heat equation in a situation when convective boundary conditions according to Newton's law of cooling hold on a surface of body and temperature of its surroundings is constant. It was elaborated so as to use data from thermographic measurements of heat propagation on a specimen plane surface which is generated pointwise by a low-power thermal impulse source. The work also includes the illustrative computational example and experimental verification conducted on the cubic specimens of cement mortar and foamed polystyrene. (C) 2010 Elsevier Ltd. All rights reserved.