Direct energy transfer (DET) method conjunction with steady state fluorescence (SSF) technique were used to study interdiffusion of polymer chains across the particle-particle junction, during film formation from high-T latex particles. The latex films were prepared from pyrene (P) and naphthalene (N) labeled poly (methyl methacrylate) (PMMA) particles and annealed in elevated time intervals above glass transition (T-g) at 180 degrees C. Monte Carlo simulations were performed to model. the N and P fluorescence intensities (I-N and I-P) using photon diffusion theory. Number of N and P photons (N-N and N-P), emerging from the front surface of the latex film are calculated when only N is excited. A novel correction method was suggested and employed to eliminate the P intensity due to the optical variation in latex film. P intensity solely from the energy transfer processes were monitored versus annealing time and was used to measure the polymer chain diffusion coefficient (D), which was found to be 5.9 x 10(-13) cm(2)/sec at 180 degrees C.