Chagas' disease (American Trypanosomiasis) affects more than 20 million people in Latin America. Almost 30% of those people may develop a chronic disease, which is expressed mainly as a chronic chagasic cardiopathy (CCC). Recent studies in Mexico have shown that 40% of patients suffering dilated cardiomyopathy do have serum antibodies against Trypanosoma cruzi. It is well known the difficulties of parasitologic diagnosis of CCC, which in less extent does exist for serologic diagnosis. Here we report a diagnostic method based on a molecular approach. It is able to recognize parasite DNA, and may have a clinical application. Two oligonucleotides (KNS1 and KNS2) designed from kinetoplast minicircle DNA, were used to amplify the hypervariable region by PCR technology. The method allowed an amplification of 0.8 to 1.5 minicircle DNA molecules, which equals 1/12,000 of parasite. When tissue DNA samples from mice infected with T. cruzi were subjected to amplification, a product was obtained that was recognized by a DNA probe specific for minicircle. These results correlate with immunohistochemical studies showing tissular parasites. Molecular diagnosis of American Trypanosomiasis, could be applied in human studies.