We combine diffusion and kinetic expressions with chemical/mechanical property relationships to develop a complete, quantitative model with no arbitrarily adjustable parameters for the time development of diffusion-limited oxidation profiles. Excellent agreement between experimental and theoretical modulus profiles for two materials (a nitrile and a neoprene) confirms our understanding of diffusion-limited oxidation and its time and temperature dependencies. The simple assumption of no time dependencies in any of the model parameters is adequate for predictions relevant to elastomer service lifetimes.