A novel in situ stress measurement technique to study the formation kinetics of multicomponent oxide thin films was developed and was applied to PbTiO3. Single phase PbTiO3 thin films were formed from the reaction between films in the deposited PbO/TiO2 multilayer. The film. stoichiometry was accurately controlled by depositing individual layers with the required thickness. The development of film stresses associated with the formation of the product layer at the PbO/TiO2 interface of the multilayers was used to monitor the growth rate of the PbTiO3 layer. It was found that growth of the PbTiO3 phase obeyed the parabolic law, and the effective activation energy was estimated to be 108 kJ/mole. It is believed that the mechanism of this reaction was dominated by grain boundary diffusion of the participating cations.