Thirty monoclonal antibodies (MoAbs) to human alpha-fetoprotein (AFP) were compared with one another by two methods: Immunoaffinity electrochromatography or additive ELISA. The first method permitted to analyse the epitopes of native AFP in solution [Abelev et al., Immunol Lett 1994;40:133-138] while the other approach also detects the epitopes of conformationally modified (partly denatured) AFP fixed on the plastic [Yazova et al., Immunol Lett 1990;25:325-330]. Competitive analysis of all MoAbs revealed 10 epitopes, 9 expressed on native AFP and 1 only on the partly denatured molecule. The cross-reactions between separate MoAbs allowed to include them into 6 distinct epitope clusters, or immunodominant groups with the characteristic patterns of reactivity. The obtained epitope map of AFP is necessary for the construction of AFP detection kits as well as for the identification of its antigenic and functional subfractions.