A novel class of high-flux and low-fouling thin-film nanofibrous composite (TFNC) membranes, containing a thin hydrophilic top-layer coating, a nanofibrous mid-layer scaffold and a non-woven microfibrous support, has been demonstrated for nanofiltration (NF) applications. In this study, the issues related to the design and fabrication of a polyethersulfone (PES) electrospun nanofibrous scaffold for TFNC NF membranes were investigated. These issues included the influence of solvent mixture ratio, solute concentration, additives, relative humidity (RH), and solution flow rate on the morphology of an electrospun PES nanofibrous scaffold, the distribution of fiber diameter, the adhesion between the PES scaffold and a typical poly(ethylene terephthalate) (PET) non-woven support, as well as the tensile properties of the nanofibrous PES/non-woven PET composite substrates. Uniform and thin nanofibrous PES scaffolds with strong adhesion to the nanofiber-PET non-woven are several of the key parameters to optimize the NF performance of TFNC membranes. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2288-2300, 2009