The kinetics of nucleation and growth of spherulites in amorphous CoSi 2 thin films of 100 nm of thickness have been studied in situ by transmission electron microscopy. The time dependence of the number of nuclei showed pronounced transient character. The growth rate was found to be constant upon isothermal annealing in the temperature range of 130 to 170 °Cin a broad interval of time. The activation energy of incorporation of growth units into the crystal lattice was found to be 23.9 kcal/mole. For the surface free energy between the crystallites and the amorphous phase the value 212 erg/cm 2 has been determined from the nucleation experiments. The nucleation was found to occur randomly in the bulk of the amorphous film with a constant rate during the transformation process as deduced from the average value n = 3.8 in the Avrami kinetic law for overall crystallization ξ = 1-exp(-kt n ).