In order to understand the dynamics of antioxidant actions of vitamin E (alpha-, beta-, gamma-, and delta-tocopherols, TocH) in biological systems, kinetic study of the formation and decay reactions of vitamin E radicals (alpha-, beta-, gamma-, and delta-tocopheroxyls, Toc center dot) has been performed in organic solvents, using stopped-flow spectrophotometry. By mixing alpha-, beta-, gamma-, and delta-TocH with aryloxyl radical (ArO center dot) in ethanol, the peaks of the UV-vis absorption due to alpha-, beta-, gamma-, and delta-Toc center dot radical appeared rapidly at ca. 430-340 nm, showed maxima, and then decayed gradually. The second-order rate constants (k(f) and 2k(d)) for the formation and decay (that is, bimolecular disproportionation) reactions of alpha-Toc center dot were determined by comparing the observed curves with the simulation ones obtained by the numerical calculation of differential equations related to the above reactions. From the results, the wavelengths of absorption maxima (lambda(i)(max)) and molar extinction coefficients (epsilon(i)) (i = 1-4) of the optical spectra were determined for alpha-Toc center dot radical. Notable solvent effects have been observed for the reaction rates (k(f) and 2k(d)) and absorption spectra (lambda(i)(max) and epsilon(i)) of alpha-Toc center dot radical. The scheme of the formation and decay reactions of alpha-, beta-, gamma-, and delta-Toc center dot radicals has been discussed based on the results obtained.