Reexpansion and contraction of polystyrene thin films supported on silicon wafer was analyzed using x-ray reflectivity (XR) measurements. It was observed that slow and fast contraction process occured in the thin films above the glass transition temperature. It was found that there is a decrease in the thermal expansivity in the well annealed thin films ∼20 nm. The results show that same contraction behavior is shown by the reexpanded films in the glassy state upon heating as the deposited films.