Ultrafine fibers of bisphenol-A polysulfone (PSF) were prepared by electrospinning of PSF solutions in mixtures of N,N-dimethylacetamide (DMAC) and acetone at high voltages. The morphology of the electrospun PSF fibers was investigated by scanning electron microscopy. Results showed that the concentration of polymer solutions and the acetone amount in the mixed solvents influenced the morphology and the diameter of the electrospun fibers. The processing parameters, including the applied voltage, the flow rate, and the distance between capillary and collection screen, were also important for control of the morphology of electrospun PSF fibers. It was suggested that uniform ultrafine PSF fibers with diameter of 300-400 nm could be obtained by electrospinning of a 20 % (wt/v) PSF/DMAC/acetone (DMAC:acetone = 9:1) solution at 10-20 kV voltages when the flow rate was 0.66 ml h(-1) and capillary-screen distance was 10 cm. (C) 2004 Society of Chemical Industry.