Tocotrienols, like tocopherols, are members of the vitamin E family. While tocopherols (T) have been studied intensively, only recently have tocotrienols (T3) received increased attention due to their special health benefits. However, these positive attributes of T3 are probably lost as a result of degradation during food storage and processing, and there is little information about their oxidation products. Of particular interest are the oxidation products of alpha-tocotrienol (alpha-T3) as this is the least thermostable T3 isomer with the highest rate of degradation. The objective of this study was therefore to develop a reliable method for the determination of the most important oxidation products of alpha-T3 along with other tocochromanol isomers. We developed a high-performance liquid chromatography method with diode array detection, fluorescence detection, and a particle beam interface electron impact mass spectroscopy in order to separate the most important oxidation products of alpha-T3 (alpha-T3 spirodimers/spirotrimers, alpha-tocotrienoldihydroxy dimer, 7-formyl-beta-tocotrienol (7-F beta T3), 5-formyl-gamma-tocotrienol (5-F gamma T3), alpha-tocotrienolquinone (alpha-T3Q), and alpha-T3Q dimers and alpha-tocotrienolquinone epoxides (alpha-T3QE)) from eight tocochromanol isomers. Furthermore, we sought to identify the as yet unknown oxidation products 5-F gamma T3, 7-F beta T3, alpha-T3Q-dimer, and alpha-T3QE. Of these, 5-F gamma T3 was fully characterized by Fourier transform infrared spectroscopy and (1)H and (13)C nuclear magnetic resonance spectroscopy.