The major factors affecting the reactivity of the important class of aminoalkyl radicals toward the addition reaction onto acrylate double bonds were studied. The rate constants of interaction, directly measured by using laser-induced photoacoustic calorimetry, range from 2.5 x 10(7) to 4.5 x 10(7) M-1 s(-1). The reactivity of these radicals was compared to that of alkyl radicals. Calculations show that the reaction enthalpy is not the driving factor. Molecular orbital calculations of the transition states clearly demonstrated the large participation of charge-transfer configurations relative to nonpolar configurations, leading to a decrease of the barrier height. Moreover a quite good correlation is found when plotting the charge-transfer character in the transition state against the ionization potential. The roles of the different factors governing the reactivity of these species were elucidated.