A quartz crystal microbalance (QCM) has been used to investigate polymer samples. The vapor sorption of three different polymer samples (poly(vinyl acetate), polybutadiene and polydimethylsiloxane) was studied. The change in resonance frequency of the quartz sensor uniformly coated with polymer films was measured as a function of the film thickness and water absorption at different temperatures. The range of linear frequency vs. mass response was determined in the absence of absorbed water. The glass transition temperature of thin poly(vinyl acetate) films (10 nm <thickness< 1000 nm) was found to be in reasonable agreement with published values for macroscopic samples.