Highly textured semicrystalline poly(ethylene terephthalate) (PET) prepared through an equal channel angular extrusion (ECAE) process was studied using small-angle X-ray scattering (SAXS), transmission electron microscopy(TEM), optical microscopy (OM), differential scanning calorimetry (DSC), and annealing tests. OM results indicate that the original spherulites are highly elongated after ECAE. SAXS and TEM results indicate that, after one ECAE pass, two types of lamellar orientations are induced: one with the lamellar normal perpendicular to the flow direction and the other tilted at an angle of approximately 45 degrees counterclockwise away from the now direction. Annealing tests suggest that interlamellar compression is the dominant mechanism for the deformation of the amorphous phase.