Kinetic and catalytic aspects of the formation of poly( ethylene terephthalate) (PET) have been studied in this work using model molecules such as 2-hydroxyethyl 4-methylbenzoate (MP), 2-hydroxyethyl 4-benzoate (MB),and 2(-hydroxyethyl 4-methylbenzoate) 4-methylbenzoate (DP), synthesized and purified in our laboratories. The methods to obtain these molecules have been described in detail. Many kinetic runs have been performed using different catalysts, such as compounds of Sb, Ti, Zr, Al, Mo (VI), Mn, Zn, Sn (IV), and Ge. We have made kinetic runs on some catalysts under different operative conditions to evaluate the effect of catalyst concentration and temperature on the reaction rate. We have observed that a second-order kinetic law is suitable for both condensation and reverse reaction. All kinetic runs have been interpreted and kinetic parameters determined. Activity can depend on catalyst concentration in a different way for each type of catalyst. Bivalent metals activity is affected by the presence of a substituent in the aromatic ring, unlike tri- and tetravalent metals. Suggestions on the reaction mechanisms conclude the work.