Abstract: A process for the preparation of anisotropic hollow fibers useful as permselective separation membranes and for producing composite membranes thereof, involves extruding a spinning dope through a spinneret that extends into a coagulation chamber maintained at subatmospheric pressure, conveying the nascent hollow fiber through a column that extends into the reduced pressure chamber, and contains at least two different abutting liquids arranged in sequence. An apparatus for conducting the process includes the vacuum chamber, the spinneret and the column that extends into the vacuum chamber and is equipped with entrance and exit ports for introduction and removal of at least two abutting liquid coagulation media.