Abstract: In a process for the purification of cytokeratin 20 (CK 20), a cytoskeletal fraction of cells containing CK 20 is produced, the proteins present therein are separated by gel electrophoresis or/and by chromatography and the CK 20 is isolated from the gel or the chromatographic fraction containing CK 20. In a process according to the present invention for the production of antibodies specific for CK 20, purified CK 20 is used for the immunization and then polyclonal or monoclonal antibodies are produced according to well-known methods. These antibodies are used for the immunologically identification of CK 20, or its .alpha.-helical central fragment obtained by proteolytic cleavage on tissue sections, in tissue homogenates and in body fluids.