Nanolayer coextrusion is an innovative process allowing to create films composed of thousands of layers of alternating polymers with individual layer thicknesses below 100 nm [1]. It has been observed that below a certain layer thickness (around 10 nm for PS/PMMA nanolayered systems), the layers tend to lose their integrity, i.e. they break spontaneously during the process [2]. The complete understanding of the physical origin of these layer breakups is therefore essential to optimize the process and reach the finest stable layers possible. The ruptures observed in these films present a certain number of analogies with the phenomenon of dewetting in thin films, widely studied in the literature. Glassy polymers deposited on a substrate with no affinity and heated above their glass transition temperature eventually broke into small droplets. In the case of monolayers or two-layer systems, both theoretical and experimental studies are numerous [3]. However, the interfacial effects in multilayer systems (ie number of layers greater than 2) are at this stage very little studied. This model study consists in measuring the dewetting kinetics of PS thin films between two layers of PMMA with no external forces applied. It constitutes a promising approach towards an understanding of the rupture phenomenon observed in the multilayer coextrusion process.