The influence of elongation and shear rates induced by the geometry of spinnerets on gas performance of PES hollow fiber membranes has been studied. Different elongation and shear rates were introduced in various spinnerets with flow angles of 60degrees, 75degrees and 90degrees by changing the flow rate of dope solution. The PES hollow fiber membranes were fabricated under the wet-spun condition without extra drawing force and their gas performances were tested by using O-2 and N-2. The flow profiles of dope solution and the elongation and shear rates at the outermost point of the outlet of spinnerets were simulated by the computational fluid dynamics model. A hypothetic mechanism is assumed to explain the effects of elongation and shear rates on the changes of conformation of polymer chain. While trying to correlate the elongation and shear rates with the gas performance of hollow fibers, we have come to some preliminary conclusions that the elongation rate has more contribution portion in permselectivity than in permeance and the shear rate has more contribution portion in permeance than in perm selectivity. (C) 2003 Elsevier Ltd.