Microporous polysulfone hollow fibers were developed with the help of chemical blowing agents by means of extrusion. Two chemical blowing agents, azodicarbonamide and 5-phenyltetrazol, were selected, and the foam morphology dependent on the concentration of blowing agent was examined by scanning electron micrograph. By means of changing the processing parameters, e.g., temperature and screw speed, the structures of the foam, usable as membrane, can be controlled.