A commercial EIA for the detection of antibody to Trypanosoma cruzi was clinically evaluated. The primary use of this test is in the diagnosis and screening of donated blood in Latin America. When compared with sera positive by xenodiagnosis, the assay had a clinical sensitivity of 100%. When tested against matched hemagglutination (HA) and immunofluorescence (IFA) results (i.e., when both tests gave negative results) the EIA had a specificity of 99.03% (305/308). The cross-reactivity of this test was determined using sera from malaria and leishmaniasis patients (obtained from Africa, ensuring that the sera did not contain Chagasic antibodies) and from schistosomiasis, toxoplasmosis, tuberculosis, syphilis, and systemic lupus erythematosus samples. The EIA was 100% specific whereas IFA or commercially available HA kits from Latin America cross-reacted with several of the samples. In this investigation, the EIA appeared to be at least as sensitive and more specific than IFA or HA in the serodiagnosis of Chagas' disease.