Thin spin-casted films of poly(ethylene terephthalate), isothermally crystallized from the melt, were studied by transmission electron microscopy. An amorphous substrate was used to get rid of unwanted nucleating influences. The lamellar scale information gained by this technique agrees well with results obtained on bulk samples despite important differences in morphology at the spherulitic scale. Starting from thin films of constant thickness, crystallization involves the migration of the polymer to the growing spherulites, resulting in the formation of polymer-depleted interspherulitic gaps. Isolated and stacked lamellae growing on top of terrace-like flat-on crystals are also noticed, allowing the direct observation of the crystalline-amorphous interphase. (C) 2003 Elsevier Ltd. All rights reserved.