Kinetics of polyesterification of maleic anhydride with polyethylene glycol (PEG) of varying molecular weights have been evaluated. The investigations have been carried out by employing heating cycles comparable to those employed in industrial processes and under nonisothermal conditions. The rate of reaction was found to decrease with increase in the chain length of the polyether. The energy of activation was estimated as 26.91, 40.25, and 47.30 Kcal/mol for PEG of molecular weights 200, 300, and 400, respectively.