Parasitemia and hystologic findings have shown that mice receiving two doses of the "vaccine" appear to react better to an infection with a virulent strain of T. cruzi than those "vaccinated" once. In the latter, the infection on the following fourth or tenth week after the immunization doesn't alter, in a substancial manner, the immune response measured by parasitemia, mortality percentage and degree of inflamatory reaction. The mice just "vaccinated" with one or two doses of the "vaccine" and noí oeing infected afterioards, didn't show any hystologic difference from the non-vaccivated ones. In those a slight focal chronic inflamatory reaction could almost always be observed at the myocardium and liver.