The dimensional recovery of biaxially oriented styrene-acrylonitrile (SAN)-copolymer films appears to consist of two second-order kinetic processes taking place in parallel. The earlier stage of recovery is dominated by a second-order process with a higher rate constant and a lower activation energy. The later stage process has a lower rate constant but with a higher activation energy. In the earlier stage, the recovery of length (machine direction) and width (transverse direction) appears to take place in parallel so that the rate constant of area recovery can be approximated as the sum of those of the length and width recoveries. In the later stage, the recovery of length and width appears to take place consecutively so that the rate constant of area recovery is the harmonic mean of those of the length and width recoveries. These findings suggest two types of conformational motion incurred simultaneously during annealing: one involves large scale chain motions that take place at the earlier stage and the other involves small scale chain motions that take place at the later stage. The large scale chain motions which govern the length and width recovery appear to occur independently, but the small scale motions appear to take place consecutively. (C) 2003 Elsevier Science Ltd. All rights reserved.