Forced convection spinning of polysulfone gas separation hollow fibre membranes was investigated. Spinneret geometry, spinning solution composition, extrusion shear, bore fluid rate, and forced convection residence time and gas rate were considered. A mass transfer model of the forced convection process was developed to help understand the effect of spinning conditions on membrane properties. Membrane pressure-normalised fluxes, selectivities and bursting pressures were discussed in terms of this new model and in terms of induced molecular orientation, polymer solution relaxation time, phase inversion (in particular skin formation) and membrane fine structural details as deduced by resistance modelling of gas transmission. (C) 2003 Elsevier B.V. All rights reserved.