Abstract: The present invention relates to a composition based on polymer and/or co-polymers of vinyl chloride including organotin salts and/or one or more divalent metal salts of a carboxylic acid or phenol, and one or more metal salts of the organic compounds of general formula A: ##STR1## in which R.sub.1 represents a linear or branched alkylene or alkenylene radical having up to 20 carbon atoms, an aralkylene radical having from 7 to 20 carbon atoms or an arylene or cycloalkylene radical having from 6 to 20 carbon atoms, the cycloalkylene radicals optionally containing carbon--carbon double bonds; these radicals optionally being unsubstituted or substituted for example by one or more or halogen atoms or hydroxyl groups or, for aryl or cycloalkylene radicals, by one or more methyl, ethyl or methoxy radicals, the above-mentioned radicals optionally modified by the presence in an aliphatic chain of one or more --O--, --CO-- or CO.sub.2 -chain members or N; R.sub.2 represents O,S,NR.sub.5 or NNHR.sub.5 wherein R.sub.