Temperature effects on thermodestructive processes in polymers are considered. The logarithm of lifetime of a linear polymer thin film on 1/T(inverse temperature) was found to be a smooth increasing curve tending to a limit at definite values of 1/T, characteristic of each polymer. Temperatures above which avalanche-like decomposition of polymers occurred were called “limiting.” To explain the dependence i t was assumed that associated and nonassociated monomer links are destroyed with different rate constants, the sequence of chemical acts in the process being the same. The rate constant of destruction of nonassociated monomer links is higher than that of associated links. Equilibrium of concentrations of associated and nonassociated monomer links is established much more quickly than the chemical reactions run. At rather low temperatures the reaction presumably runs at chain ends. As the temperature increases, the number (concentration) and the length of blocks consisting of nonassociated monomer links increase, also. When the length of such a block reaches a definite value, a break reaction occurs, the break constant increasing with the increase of the block length. The dependence of the process rate on temperature is determined both by concentrations of blocks of various length and by the temperature dependence of break rate constants. At a definite temperature the reactions presumably at the chain ends are substituted by chance reactions. At temperatures when intermolecular interactions can be neglected, thermodynamically unstable “polymer” gas appears which decomposes in an avalanche-like manner.