A novel in-situ stress measurement technique to study the formation kinetics of multi component oxide thin films was developed and was applied to PbTiO₃. Single phase PbTi 0₃ thin films were formed from the reaction between films in the deposited PbO ITi0₂ multilayer. The film stoichiometry was accurately controlled by depositing individual layers of the required thickness. Development of film stresses associated with the formation of the product layer at the PbO/Ti0₂ interface of the multilayers was used to monitor 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.