The old controversial idea of structures in molten amorphous polymers is being accepted with theoretical and experimental evidence. Wool's twinkling fractal theory of the glass transition and recent atomic force micrographs are convincing proof of the dynamic, solid aggregate presence below and above T-g. This article offers detailed analysis of the experimental data from high-pressure dilatometry, as well as from the oscillatory shear tests in the glassy and the molten state of polystyrenes. The results indicate the presence of a transient structure at T > T-g; transient as it depends on the structure of the vitreous polymer and the rate of heating it across T-g. Thus, molten polymer is not always at the thermodynamic equilibrium. (C) 2011 National Research Council Canada.(dagger) J Polym Sci Part B: Polym Phys 49: 1369-1380,2011