Abstract: Poly-dihydro-2,6-dimethylpyridine-3,5-dicarboxylesters of general formula (I) ##STR1## in which A, B, m, n, k, j, R, R.sup.1 and R.sup.2 have the meanings defined in the text, useful as thermal stabilizers for synthetic polymers, in particular for polyvinylchloride-based masses.The compounds of formula (I) are preferably used in combination with the usual stabilizers based on organic metal derivatives. They can also be used combined with agents which exert a synergic action in maintaining a low color of manufactured articles subjected to heating, and in particular with betadicarbonyl compounds of formula (II):R.sup.3 --CO--CH.sub.2 --CO--R.sup.4 (II)in which R.sup.3 and R.sup.4 have the meanings defined in the text, in masses containing organic calcium and zinc salts as basic stabilizers.