A method for quantitative evaluation of kinetic constants in Ziegler-Natta and metallocene olefin polymerizations is presented. The method comprises some fundamental steps, which include the initial design of a statistical experimental plan, the execution of the designed experiments, the development of simple mathematical models to describe the polymerization, and the estimation of kinetic parameters from available rate, gel permeation chromatography, and NMR data. The method is applied to the slurry propylene polymerization, using a conventional first generation Ziegler-Natta catalyst, in a lab-scale polymerization reactor. It is shown that the proposed method allows the successful interpretation of experimental olefin polymerization data and the quantitative evaluation of kinetic constants, which can be inserted into a process simulator to provide an accurate picture of actual industrial plant behavior.