Nonradiative energy transfer is used to examine the interdiffusion of polymer molecules during annealing of a latex film at 160-degrees. Steady state fluorescence measurements are taken at each step of film formation. The film was prepared from a mixture of naphthalene-(donor) and pyrene-(acceptor) labelled poly(methyl methacrylate) latex particles. During the annealing processes, the ''optical density'' (index of refraction) of the latex film changes considerably. Corrections of the donor and acceptor intensities are made and corrected acceptor intensity is treated by the classical and reptation diffusion models at long and short time regions respectively.