An experimental investigation of the fiber morphology change of fibers prepared by a dual-capillary electrospinning system, operated in the cone-jet mode, was carried out for poly(vinyl acetate) polymers of three molecular weights. The substrate morphology of the electrospun poly(vinyl acetate) could be changed significantly when the polymer's molecular weight, concentration, solvent, and outer liquid flow rate were varied. The onset of bead-to-fiber transition was determined by the critical chain overlap concentration. For solutions with a high concentration, the fiber diameter and surface were significantly affected by the physical properties of the solvents. To produce fibers of small diameter, electrospinning with a higher conductivity solution was desirable. On the other hand, a high-conductivity solution needed to be avoided to keep the fiber uniform in diameter and smooth on the surface. The comparison of electrospun fibers produced by both single-capillary and dual-capillary systems was also addressed. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 204-215, 2010