This paper reports the effects of changing membrane formation parameters, including polymer concentration, evaporation time and post casting annealing, on transport through integrally skinned asymmetric polyimide organic solvent nanotiltration membranes. The molecular weight cut off curve was most significantly affected by changes in the polymer concentration of the casting solution. Flux was observed to be sensitive to variations in several formation parameters. Scanning electron micrographs show three different morphologies present in the membranes, with a nanoporous nodular structure present at the top surface. The experimental transport data was interpreted using the intrinsic membrane parameters of permeability and pore size in the solution diffusion and pore flow models, respectively. (c) 2007 Elsevier B.V. All rights reserved.