The kinetics of the reaction between cyclopentene and an aqueous solution of hydrogen peroxide under phase-transfer catalysis conditions has been studied. The activation energies of the successive stages of cyclopentene epoxidation to 1,2-epoxycyclopentane and the hydration of the resulting epoxide to 1,2-cyclopentanediol have been found, and the orders of the reactions with respect to the reactants have been determined. A mathematical model of the process that adequately describes the available experimental data in the entire range of reactant concentrations has been proposed.