Submicrometer fibers of poly(vinyl alcohol) (PVA) and chitosan oligosaccharide [COS; i.e., (1-->4)-2-amino-2-deoxy-beta-D-glucose were prepared by an electrospinning method with aqueous solutions with polymer concentrations of 7.5-15 wt %. Scanning electron microscopy, Fourier transform infrared, X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis were used to characterize the morphology and properties of the PVA/COS fibers. The PVA/COS mass ratio, the total polymer concentration, and processing parameters such as the applied voltage and capillary-to-collector distance played important roles in controlling the fiber morphology. Fourier transform infrared and X-ray diffraction data demonstrated that there were possibly hydrogen bonds between COS and PVA molecules that weakened the interactions in COS and improved the electrospinnability of PVA/COS. Moreover, with a higher percentage of COS in the PVA/COS blend fibers, superior thermal stability could be obtained. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 132-140, 2009