The steady-state fluorescence technique was used to study the evolution of transparency during film formation from high-T latex particles. The latex films were prepared from pyrene-labelled poly(methyl methacrylate) particles and annealed in 10 min time intervals above the glass transition temperature (T-g) Scanning electron microscopy was used to detect the variation in physical structure of annealed films. Monte Carlo simulations were performed for photons diffusing the latex films and the number of emitted and scattered photons was calculated. The crossing density of polymer chains at the particle-particle interface was found to depend linearly on (time)(1/2). The activation energy for back-and-forth motion of a reptating polymer chain was measured and found to be 29 kcal mol(-1). The corresponding frequencies of a reptating chain were between 1.5 and 42 s(-1) above T-g.