The transition state theory of diffusion has been applied to the rate of oxidation of metals as a function of temperature. The expression involves an entropy of activation as well as the energy of activation. Experimental results indicate that the oxidation of iron, stainless steel and copper follows the parabolic law for certain temperature ranges and pressure ranges after a certain initial period. The parabolic rate law constants are shown to follow a straight line when log K is plotted against . Energies of activation of 22,600, 29,600 and 24,900 are found for iron, stainless steel and copper respectively. Entropies of activation are calculated to be −31, −35 and −6.8 for iron, stainless steel and copper respectively. The importance of entropy factor is briefly considered.