Thermal decomposition of tocopherols (Toc) in various vegetable oils, and/or oxidative stabilities following heat treatment were investigated. The oils or mixtures of soybean oil and methyl stearate or oleate were heated in a glass tube (2.7 × 20 cm) at 180°C. Residual amounts of Toc in oils and oxidative stabilities were determined by HPLC and oven tests, respectively. The degree of thermal decomposition of Toc in heated oils was found much higher in high oleic safflower, in high oleic sunflower, and in low erucic rapeseed oils than in low oleic safflower, and sunflower and high erucic rapeseed oils. No significant differences could be found in the thermal decomposition of Toc in four kinds of palm oils (palm oil, palm olein, palm stearin, and hardened palm oil). The thermal decomposition of Toc in mixtures of soybean oil and methyl stearate or oleate increased with the concentrations of stearate and oleate.