A spray-assisted, 2-step interfacial polymerization (IP) of trimesoyl chloride (TMC)/m-phenylenediamine (MPD) was proposed for the preparation of polyamide (PA) membranes. In the first step, TMC/hexane solutions were sprayed onto MPD-impregnated polysulfone (PSI) supports for 10-60 s, followed by a second step where the first-step membranes made contact with the TMC/hexane solutions. It is noteworthy that water permeability was increased with spray time in the first step of the 2-step IP, showing approximately doubled values at the spray time of 20-30s, compared with 1-step PA/PSf composite membranes, while NaCl rejections were practically unchanged. With longer spray time (3060 s), water permeability decreased while NaCl rejection remained at the same level. A characterization of 1- and 2-step PA membranes, including FE-SEM and ATR-FTIR, revealed the formation of multilayered ridge-and-valley structures of polyamide from the spray-assisted IP steps, and it is suggested that the increased water permeability have been caused by the increased interfacial surface area of the 2-step PA membranes. (C) 2013 Elsevier B.V. All rights reserved.