A simple one-step method of preparing of ultrafine poly(acrylonitrile) (PAN) fibers containing Ag nanoparticles was developed. Ag+ ions in a PAN solution were directly reduced to produce Ag nanoparticles and the resulting solution was. electrospun into ultrafine PAN fibers. N,N-dimethylformamide (DMF) was used as a solvent for PAN as well as a reducing agent for the Ag+ ions. The numbers of Ag nanoparticles in the ultrafine PAN fibers were increased as the amount of AgNO3 was increased from 0.05 to 0.5 wt.%. The Ag nanoparticles were all sphere shaped with an average diameter of less than 5.8 nm. (C) 2005 Elsevier B.V. All rights reserved.