In this study, we examined the immunochemical properties of the 35- and 50-kDa (35/50-kDa) surface glycoconjugates expressed on the surface of metacyclic trypomastigotes of Trypanosoma cruzi using three different monoclonal antibodies directed to this component. The 35/50-kDa surface antigen was expressed by metacyclic trypomastigotes of 11 different strains of T. cruzi and displayed a significant degree of molecular polymorphism. Results of immunoblotting and complement-mediated lysis were consistent with such diversity. Different monoclonal antibodies reacted with distinct epitopes on the 35/50-kDa antigen, which is resistant to proteases and behaves as an amphiphilic component.