Experimental data on the decomposition of alkyl radicals in the gas phase of the type (RCH2CH2)-H-center dot --> RCH=CH2 + H-center dot were analyzed in terms of the method of crossing parabolas. The parameters characterizing such decomposition were calculated. The activation energy E-e0 for the thermoneutral degradation reaction was shown to depend on the radical structure. The degradation of the radicals (RCH2CH2)-H-center dot, CH2=(CRCH2)-H-center dot, (PhCHCH2R)-H-center dot, and CH2=(CCH2R)-C-center dot is characterized by E-e0= 81.6, 85.9, 85.9, and 115.2 kJ mol(-1), respectively. The semiempirical algorithm for calculation of geometric parameters of the transition state for reactions of hydrogen atom addition to olefins was extended to the degradation reactions of alkyl, aminoalkyl, and ketyl radicals. The kinetic (activation energies) and geometric (interatomic distances in the transition state) reaction parameters were calculated for the decomposition reactions of various alkyl, alkylaromatic, aminoalkyl, and ketyl radicals.