Thermal decomposition changes occurring in cholesterol esters of ferulic and sinapic acids were studied by means of TG/DTA. A one-stage decomposition has been established for their thermal degradation in the temperature interval from room temperature to 500 degrees C. The carbon skeleton of the esters determines their thermal stability. By means of TG/DTA studies it has been demonstrated that 4-hydroxy-3-methoxy cholesteryl cinnamate and 4-hydroxy-3,5-dimethoxy cholesteryl cinnamate at content up to 0.0033 mM reduce chain length of tetralin hydroperoxide (0.427 and 0.457 mM) thermal decomposition but inhibition of 'induced' component is not observed. These eaters (at content more than 0.008 mM) demonstrated catalytic effect of free radical induced decomposition as a result of reactions generating radicals. 3-Hydroxy-4-methoxy cholesteryl cinnamate (from 0.0089 to 0.0148 mM) suppress tetralin hydroperoxide (0.457 mM) free-radical-induced decomposition.