The kinetic analyses for thermal products of alpha-, gamma- and delta-tocopherols during heating as functions of temperature and time were studied. Alpha-, gamma- and delta-tocopherols dissolved in glycerol were heated at $100{sim}200^{circ}C$ for $5{sim}60$ min. The thermal products were separated by hexane extraction and analyzed by HPLC using a reversed phase ${mu}-Bondapak$ $C_{18}-column$ with two kinds of elution solvents in a gradient mode. The formation kinetics of thermal products of tocopherols followed a first-order kinetic model. The formation rate of thermal products of tocopherols was dependent on heating temperatures and heating times. The activation energy and enthalpy for the thermal products of ${gamma}-and$ ${delta}-tocopherols$ were higher than those for ${alpha}-tocopherol$ as in the case of the oxidative degradation kinetics of tocopherol. The magnitude order of the activation energy was ${gamma}->{delta}->{alpha}-tocopherol$.