NOVELTY - A process for the preparation of hollow fibers comprises: (1) preparation of a porous template material; (2) introduction of at least one polymer containing liquid into the pores of the template material so that the pore walls are wetted by the liquid, but not completely filled by it; (3) solidification of the liquid; and (4) optionally, at least partial removal of the template material.    USE - The hollow fibers are useful for preparation of nonwovens or fabrics (claimed), in medical equipment, e.g. artificial lungs, microeletronics, superconductor technology, medical separation technology, capillary electrophoresis, fuel cells, batteries, electrochemical reaction equipment (claimed), as microreactors, for protein storage, drug administration systems, as fillers, chip production (claimed), as porous materials in combinatorial chemistry (claimed), and in the clothing industry (claimed).    ADVANTAGE - The process can be applied to both functionalized and non-functionalized polymers, and to mixtures of polymer and non-polymer materials. The process also avoids some of the drawbacks of previous processes, e.g. high cost, restriction to a narrow range of starting materials in production of nano-tubes.    DETAILED DESCRIPTION - A process for the preparation of hollow fibers of external diameter 10-100 microm containing at least one polymer comprises:    (1) preparation of a porous template material;    (2) introduction of at least one polymer containing liquid into the pores of the template material so that the pore walls are wetted by the liquid, but not completely filled by it;    (3) solidification of the liquid; and    (4) optionally, at least partial removal of the template material.    INDEPENDENT CLAIMS are also included for:    (1) Porous materials, preferably polymer membranes, metal oxides, ceramics, metals, or semi-metals, especially Al oxide, Si oxide, obtainable as below;    (2) Hollow fibers of external diameter 10-100 nm containing at least one polymer, obtainable as below;    (3) An arrangement of hollow fibers, e.g. parallel hollow fiber; and    (4) A powder consisting of hollow fibers.