Biodegradable non-woven mats of poly(lactic acid) (PLA) and chitosan (CS) were fabricated by the coaxial electrospinning process. These non-woven mats are composed of PLA/CS core/shell composite nanofibers, in which PLA and CS form the core and shell layers, respectively. CS of high molecular weight could not be electrospun on its own because of its high viscosity in solution and its polycationic possession. The coaxial electrospinning method was able to facilitate the fabrication of double-layer PLA/CS composite nanofibers by employing a PLA layer in the core and a CS layer in the shell part. Transmission electron microscopy (TEM) studies and contact-angle measurements indicated the core/shell structure of the composite nanofibers fabricated with shell and core feed rates of 5 mu L/min and less than 2 mu L/min, respectively. The PLA/CS core/shell composite nanofibers showed antibacterial activity against Escherichia coli: hence it can be used as antibacterial materials in fields such as biomedical and filtration areas. (C) 2011 Elsevier Ltd. All rights reserved.