A series of hollow-fiber membranes was produced by the dry-wet spinning method from PEEKWC, a modified poly(ether ether ketone) with good mechanical, thermal, and chemical resistance. The fibers were prepared under different spinning conditions, varying the following spinning parameters: polymer concentration in the spinning solution, height of the air gap, and bore fluid composition. The effect of these parameters on the water permeability, the rejection of macromolecules (using dextrane with an average molecular weight of 68,800 g/mol), and the morphology of the membranes was studied. The results were also correlated to the viscosity of the spinning solution and to the ternary polymer/solvent/nonsolvent phase diagram. The morphology of the cross section and internal and external surfaces of the hollow fibers were analyzed using scanning electron microscopy (SEM). All membranes were shown to have a fingerlike void structure and a skin layer, depending on the spinning conditions, varying from (apparently) dense to porous. Pore size measurements by the bubble-point method showed maximum pore sizes ranging from 0.3 to 2 mum. Permeability varied from 300 to 1000 L/(h(-1) m(-2) bar) and rejection to the dextrane from 10 to 78%. The viscosity of polymer solutions was in the range of 0.2 to 3.5 Pa s. (C) 2003 Wiley Periodicals, Inc.