Abstract: The kinetics of liquid-phase oxidation of cumene with air using cn-mene hydroperoxide as an initiator has been studied in the temperature range of 100° to 130° C for semi-batch operation. According to the chain free-radical mechanism for liquidphase oxidation of hydrocarbons and the assumed mode for the decomposition of cumene hydroperoxide, a kinetic model for the steady chain-propagation period is derived. On the basis of the experimental results obtained, the rate constants and the apparent activation energy for liquid-phase oxidation of cumene and for the side reaction of decomposition of hydroperoxide are determined. The concentrations of cumene and its hydroperoxide calculated from the kinetic model fit in satisfactorily with the experimental results. In this paper the induction period for the semi-batch operation and the effects of reaction temperature on the conversion of cumene and on the selectivity to cumene hydroperoxide are also discussed.