In this work the polarization and hysteresis response of Lead Zirconate Titanate (PZT) ferroelectric thin films was studied in relation to the variation on temperature, stress, electric field and the content of non-ferroelectric impurities by using a Monte Carlo simulation. The simulation was basedon a DIFFOUR Hamiltonian that takes into account the effect of uniaxial stress, in addition to the nearest neighbor dipoles interaction and the effect of an external electric field. The obtained results for hysteresis loops and polarization curves correspond with reported experimental data for this material.