Hybridoma cell lines secreting monoclonal antibodies against the Tulahuén strain of Trypanosoma cruzi were produced by the fusion of SP2/O-Ag 14 myeloma cells with spleen cells from mice immunized with irradiated metacyclic trypomastigotes. Twenty of the monoclonals synthesized by the hybridomas were identified as IgM, 2 as IgG1, 10 as IgG2a, 3 as IgG2b, 4 as IgG3, 1 as IgE, and 1 as IgA. Twenty-three of these antibodies had kappa light chains and 18 showed delta chains. Twelve of the monoclonals agglutinated metacyclic trypomastigotes without additional concentration and 4 of these precipitated antigens in extracts of T. cruzi metacyclic or epimastigote stages. One monoclonal precipitated an epimastigote antigen, while another reacted with a metacyclic antigen, and 2 antibodies formed precipitin lines with antigens of both stages. Agglutinin assays performed to characterize surface antigenic specificities of the 12 monoclonal antibodies showed that 2 reacted only with the metacyclic stage of the Tulahuén strain. Two monoclonals agglutinated both metacyclic trypomastigotes and epimastigotes of the Tulahuén strains. Three antibodies caused clumping of metacyclics and epimastigotes of the Tulahuén, Raccoon V, and Corpus Christi strains of T. cruzi, while a fourth also reacted with bloodstream trypomastigotes. One monoclonal detected identical epitopes on metacyclics and epimastigotes of T. cruzi and epimastigotes of Trypanosoma musculi, while 2 antibodies reacted with metacyclics, epimastigotes, and bloodstream trypomastigotes of the Tulahuén and Raccoon V strains and the bloodstream stage of T. musculi. One antibody agglutinated all stages and strains of T. cruzi, T. musculi, and Trypanosoma lewisi which were tested.(ABSTRACT TRUNCATED AT 250 WORDS)