Poly(L-lactide) (PLLA) and a PLLA/Poly(D-lactide) (PDLA) blend (50/50 wt.%) were electrospun into nanofibers. Electron beam (e-beam) irradiation of the electrospun PLLA and blend nanofibers was used as a method to alter their structures and surface properties. The crystalline structures of the nanofibers before and after irradiation were investigated by differential scanning calorimetry. Tensile tests of the aligned nanofibers were also performed to determine the effects of irradiation on the mechanical properties of the nanofibers. The hydrophilicity of the nanofibers was determined by water contact angle measurements, while any degradation of the fibers caused by irradiation could be detected by intrinsic viscosity measurements. The e-beam irradiation method was able to improve the surface hydrophilicity of the PLLA and blend nanofibers, although bulk degradation was inevitable. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.