The meso/nanostructure of UHMWPE fibers manufactured using different processing conditions is explored through atomic force microscopy (AFM) and wide-angle X-ray diffraction (WAXD). Characteristic dimensions of sub-filament microstructure are quantified at the fiber surface and the fiber interior. These measurements are compared to crystalline parameters determined using WAXD. Observation of junctions between microfibrils suggests the original gel network from which the fiber was drawn remain in the final product. For fibers having undergone greater drawing, the fiber surface reveals the presence of large-scale epitaxial features oriented perpendicular to the direction of drawing. Annealing experiments show that epitaxial structures undergo thickening at temperatures >120 degrees C. Examining fiber cross-sections reveals a network of microfibrils that appear to undergo consolidation with increased drawing. The evolution of the structural hierarchy of these fibers is discussed in the context of its implications for optimization of processing both fibers and their composites. (C) 2015 Elsevier Ltd. All rights reserved.