The diffusion processes and growth kinetics of the Mo3Si silicide layer occurring at annealing the Mo5Si3/Mo diffusion couple between 1180 and 1800 degrees C were studied by electrothermography. The experimental results are supplemented with calculations on the behaviour of the initial Mo5Si3/Mo diffusion couple on the basis of the reaction diffusion model describing the transformation of the Mo5Si3 layer into a Mo3Si one. The values of the parabolic growth constant for Mo3Si layer were determined and the silicon diffusion coefficient in the Mo3Si phase was calculated: D=0.165 exp[(-247 +/- 10)/RT], cm(2)/s, where the activation energy is expressed in terms of kJ/mol. (C) 2007 Elsevier B.V. All rights reserved.