Human Chagas' disease, caused by the protozoan Trypanosoma cruzi, is associated with pathological processes whose mechanisms are not known. To address this question, T cell lines were developed from chronic chagasic patients peripheral blood mononuclear cells (PBMC) and cloned. These T cell clones (TCC) were analyzed phenotypically with monoclonal antibodies by the use of a fluorescence microscope. The surface phenotype of the TCC from the asymptomatic patient were predominantly CD4 positive (86%). On the contrary, the surface phenotype CD8 was predominant in the TCC from the patients suffering from cardiomegaly with right bundle branch block (83%), bradycardia with megacolon (75%) and bradycardia (75%). Future studies will be developed in order to identify the antigens eliciting these T cell subpopulations.