The reactive growth of tantalum silicides was studied by means of Ta-Si diffusion couples annealed at 1250-1350 degreesC for 2-36 h. Two layers, corresponding to Ta5Si3 and TaSi2, were observed in the diffusion zone. The TaSi2 layer was about 1 order of magnitude thicker than the Ta5Si3 layer. Formation of the compounds Ta3Si and Ta2Si was not detected. probably because their growth rate is very small. The concept of rate constant of the second kind was used to describe the growth kinetics of the silicides. For Ta5Si3, different values of the rate constant of the second kind can be obtained depending on the boundary conditions adopted at the Ta/Ta5Si3 interface. The rate constant of the second kind was related to diffusion properties and thermodynamic stability of the given phase. Average values of the interdiffusion coefficient were calculated for the Ta5Si3 and TaSi2 Compounds. The corresponding activation energy is similar to450 kJ mol(-1) for Ta5Si3 and similar to560 kJ mol(-1) for TaSi2.