Miniemulsion polymerization is a powerful technique to produce a whole variety of latexes with controlled colloidal and chemical properties, which has gained an increasing importance in the past years. For many applications, the following of the kinetics of polymerization is of crucial importance. In this study, we developed a technique based on the use of fluorescent probes that could be a very promising noninvasive method to follow the reaction in situ. It was possible to follow qualitatively the kinetics of methyl methacrylate (MMA) polymerization by measuring the photophysical properties of fluorescent probes sensitive to the modification of the viscosity of the microenvironment along the reaction course. Two fluorescent sensors have been considered: 1,1-dicyano-4-(4'-dimethylaminophenyl)-1,3-butadiene) and pyrene. In this article, we will show that using these two different fluorescent probes allow the detection of MMA polymerization in miniemulsion. The results will be compared with a classical NMR method. This method could be easily adapted to different monomers. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 219-224, 2011