The kinetics of the high-pressure ethylene polymerization initiated by di-tert-butyl peroxide were measured via quantitative near-infrared spectroscopy at temperatures between 130°C and 165°C to a maximum pressure of 3 kbar. The overall polymerization rate was found to be first order in ethylene concentration and of the order 0,5 in peroxide concentration. The overall activation energy and the overall activation volume were determined to be E0 = 107,2 ± 7,5 kJ · mol-1 and Δ V0≠ = - 17,5 ± 5,0 cm3 · mol-1, respectively. From the overall quantities and from the decomposition rate of di-tert-butyl peroxide determined in independent spectroscopic high-pressure high-temperature experiments, kp · kt-1/2 (kp and kt are the propagation and termination rate constants, respectively) and the corresponding activation parameters, Ep - 1/2 Et and Δ vp≠ - 1/2 Δvt≠, were derived for the high-pressure ethylene polymerization. These data enable the overall polymerization rate to be determined also for high-pressure ethylene polymerizations initiated in any different way, provided the initiation rate law is known. The procedure is illustrated for the ethylene polymerization initiated by tert-butyl peroxypivalate.