The effects of various melt-electrospinning parameters on the morphology and fiber diameter of polypropylene of different tacticities were studied. The effect of the electric field strength at various melt flow indexes of polypropylene on fiber uniformity, morphology, and diameter was measured. It was shown that the molecular weight was the predominant factor in determining the fiber diameter of the collected fibers. Observations prove that the tacticity also influences the fiber diameter. Atactic polymers having molecular chains incapable of crystallization tend to produce larger diameter fibers than isotactic polymers capable of crystallization even at lower molecular weights. The polymer volume, at a given time, supplied to the electric field affected fiber diameter. Those systems supplying the smallest volume, at a given time, produced the smallest fiber diameter. (C) 2004 Elsevier Ltd. All rights reserved.