Infection of BALB/c mice with chemically induced metacyclic forms of Trypanosoma cruzi clone Dm28c led to characteristic changes of experimental Chagas' disease, with protracted but marked parasitemia, intense splenomegaly, and splenic T cell hyporeactivity to TcR;CD3-dependent stimulation. Infection of BALB/c mice with either chemically induced or triatomine-derived Dm28c metacyclic forms led to comparable parasitemias, a synchronous increase in the number of splenic large lymphocytes, and a similar reduction in T cell responsivity to immobile anti-CD3 antibody. A marked and selective reduction in the level of CD8 expression per cell was also seen in mice infected with either form of metacyclic parasites. Large inflammatory mononuclear cell infiltrates were present in the hearts of mice infected with either chemically induced or insect vector-derived metacyclic forms, at both acute and chronic stage, with predominance of CD8 over CD4 T cells in the lesions, in both cases. These results indicate that infection with chemically induced metacyclic forms of T. cruzi can be a useful model of Chagas' disease, resembling infection caused by the insect vector.