Lipid microparticles, containing 30% and 50% (w/w) propafenone hydrochloride as the active molecule and cetearyl alcohol and Pluronic F68 as excipients, were prepared by Hot Air Coating (HAC). The aim of the work was to identify the kinetics and the mechanism of the drug release process from these microparticulate systems. The application of the Weibull model to the release data from each single fraction of microparticles suggests that a diffusive mechanism governs drug release from microparticles. Thus, we proposed and applied a release kinetic model to the experimental data that takes into account the diffusion as the predominantly mechanism of drug release. The model proposed is a modified version of the exponential equation in which the product of the apparent release rate constant K, specific for each drug/excipient mixture, and the area-to-volume ratio of particles was used. The K values of single fractions of HAC microparticles (coded K(fr)) are very similar to those of the mixtures of particles obtained from the process (coded K(pool)). Using the K(pool) constants, the release behaviour of ensembles of different size microparticles of well-known composition was predicted. The strength of the model was proved by the good fitting of the experimental release data versus those predicted (R(2)> or =0.997).