The influence of two not harmful and ecologically non-hazardous antioxidants from the group of sterically screened phenols - lrganox 1010 and Topanol CA, was studied, as well as that of "natural" antioxidant tocopherol acetate and the epoxy stabilizer Edenol D-81. 23 samples were prepared as films, containing PVC and the additives studied. The degradation took place in real atmosphere at 180 ^oC and was followed by continuons potentiometry. From the kinetic curves thus obtained the values of thermal stability and of the gradient dx/dt were obtained. The proposed kinetic models were used for obtaining the corres-ponding rate constants which enable a mutual comparison of the efficiency of sterically screened phenolic antioxidants with tocopherol acetate. The results of calculations confirm that in presence of CaO or Edenol D-81 the trapping ability of Irganox 1010 increasis. The most potent antioxidant is tocopherol acetate which has the same ability to terminate the growth of polyene sequences as Irganox 1010 and is a slightly stronger trapping agent for HCI.