Two monoclonal antibodies raised against native horse alcohol dehydrogenase (HADH) bind preferentially to the enzyme attached to solid supports and recognize the denatured and carboxymethylated HADH subunits. Both antibodies cross-react with the human class I isoenzymes but do not recognize the class III ADH isoenzyme. Protease digestion, electrophoresis and HPLC have been used to identify the linear epitope which is contained in the sequence Pro344-Glu357 of the HADH subunit.