When amorphous polymers of same type are brought into contact at temperatures above the glass transition, the interface gradually heals and junction boundaries eventually disappear. Here we used a steady-state fluorescence technique to examine the healing and interdiffusion of polymer molecules during annealing of latex film above the glass transition. The film was prepared from a mixture of naphthalene-(donor) and pyrene-(acceptor) labelled poly(methyl methacrylate) latex particles. We report that during the annealing processes the transparency of the film changed considerably. Healing temperature (T-H) and time (tau(H)) were measured when the latex film became almost transparent. Above T-H interdiffusion of polymer chains was observed by detecting the energy transfer from excited naphthalene to pyrene molecules. Healing and diffusion activation energies were calculated and found to be 9.84 kcal mol(-1) and 30 kcal mol(-1), respectively, for the annealed latex film samples.