In this study, poly(epsilon-caprolactone)-based polyurethane (PCL-PU) nanofibers containing Ag nanoparticles for use in antimicrobial nanofilter applications were prepared by electrospinning 8 wt% PCL-PU solutions containing different amounts of AgNO3 in a mixed solvent consisting of DMF/THF (7/3 w/w). The average diameter of the pure PCL-PU nanofibers was 560 nm and decreased with increasing concentration of AgNO3. The PCL-PU nanofiber mats electrospun with AgNO3 exhibited higher tensile strength, tensile modulus, and lower elongation than the pure PCL-PU nanofiber mats. Small Ag nanoparticles were produced by the reduction of Ag+ ions in the PCL-PU solutions. The average size and number of the Ag nanoparticles in the PCL-PU nanofibers were considerably increased after being annealed at 100 degrees C for 24 h. They were all sphere-shaped and evenly distributed in the PCL-PU nanofibers, indicating that the PCL-PU chains stabilized the Ag nanoparticles well. (C) 2008 Elsevier B.V. All rights reserved.