In the electrospinning of polymer nanofibers, an electrically driven jet of polymer solution travels to a grounded target to be collected. The morphology of the resulting nanofibers can be manipulated through process parameters, though little work has been done to correlate electrospinning parameters with those of the free-jet flow of pure liquids. This is essential when the nanofibers hold entrained beaded structures indicative of jet breakup. The effects of applied voltage and solution concentration on the fiber morphology of electrospun aqueous solutions of poly(ethylene oxide) were investigated. Solution concentrations of 4-8 wt % were used along with voltages of 4.5-11 kV to produce nanofibers with and without entrained beads. It was determined that the calculated Weber number for each condition correlated well with the resulting morphology. These results may suggest that Weber number may also be used to predict nanofibers morphology in the electrospinning of other polymer systems. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 880 885, 2011