We have observed hysteretic loops in the structural phase transition Of VO2 thin films using Raman microscopy. A model is presented concerning the size distribution to illustrate the relative Raman intensity-temperature hysteretic loops in the VO2 films. We also found the different changing behavior of A(g) and B-g phonon modes during the phase transition process. (C) 2004 Elsevier B.V. All rights reserved.