Antibody levels to Trypanosoma cruzi were compared in asymptomatic individuals infected with the parasite as well as those with different forms of chronic Chagas' disease of varying severity. The following three serologic tests were used: complement fixation, direct agglutination with previous treatment of the serum with 2-mercaptoethanol, and the enzyme-linked immunosorbent assay. The clinical groups tested included individuals with (a) a positive serology but no symptoms and without evidence of chronic disease (indeterminate form); (b) mega disease (groups I, II, III, and IV); (c) cardiomyopathy (mild, moderate, and severe); and (d) those with both mega disease and cardiomyopathy (combined form). The mean enzyme-linked immunosorbent assay and complement fixation antibody levels among the various clinical groups showed no statistical differences. With the direct agglutination test patients with mega disease and those with severe cardiomyopathy had slightly higher mean titers than patients in the indeterminate group and those with mild or moderate cardiomyopathy. While there may be possible reasons for these differences, the biological relevance of the findings was concluded to be of dubious significance.