Experimental data on the gas-phase degradation of alkyl radicals of the type (RCHRCH2)-C-1-C-2-H-. -> CHR2 = CH2 + R-1 were rationalized in terms of the method of crossing parabolas. The parameters characterizing the degradation were calculated. The semiempirical algorithm for the calculation of the geometric parameters of the transition state of methyl radical addition to olefins is extended over the reactions of degradation of alkyl radicals. The kinetic (activation energy) and geometric (interatomic distances in the transition state) parameters of the reaction were calculated for the degradation of alkyl radicals of various structures. For the degradation reactions involving the detachment of the methyl radical, a linear correlation between the transition-state interatomic distance r(#)(C...C) and the enthalpy of the reaction Delta H-e was revealed: r(#)(C...C) x 10(10)/m = 2.37 - 1.19 x 10(-2) Delta H-e/kJ mol(-1). A similar relationship is observed for the ethylene elimination reactions: r(#)(C...C) x 10(10)/m = 2.40 - 1.46 x 10(-2) Delta H-e/kf mol(-1). The enthalpies, activation energies, and transition-state interatomic distances for the degradation of alkyl radicals involving H-. and (CH3)-H-. detachment are compared.