Communication: The melting temperature (Tm,) of thin poly[ethylene-co-(vinyl acetate)] films coated on a silicon wafer was investigated. Ellipsometry was used to measure the Tm,which was found to decrease dramatically when the thickness of the film is less than 300 Angstrom. The relationship between the lamellar thickness and the Tm, was thought to be responsible this thickness dependence of the Tm, in thin polymer films.