A model of uncatalyzed oxidation of cyclohexane in the liquid phase, including both kinetics and mass transfer, is presented. The reaction rate constants as well as the activation energies were determined on the basis of the experimental results obtained in a laboratory reactor with carefully passivated inner surface. A mathematical model of an industrial reactor for the cyclohexane oxidation is also presented. The results of the uncatalyzed cyclohexane oxidation simulations are compared with the data from the industrial reactor. The results of the present work have been used for modernization of the Polish CYCLOPOL process, and enabled the development of CYCLOPOL-bis [Gruszka, M., Krzysztoforski, A., Moniuk, W, Oczkowicz, S., Pohorecki, R., Wierzchowski, P.T. and Zylinski, M., 2005, CYCLOPOL-bis - the second youth of the Polish process for oxidation of cyclohexane, Przemysl Chemiczny (Chem Ind), 84: 493-502 (in Polish)]. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.