Peritoneal macrophage activation as measured by H2O2 release and histopathology was compared between Swiss mice and Calomys callosus, a wild rodent, reservoir of Trypanosoma cruzi, during the course of infection with four strains of this parasite. In mice F and Y strain infections result in high parasitemia and mortality while with silvatic strains Costalimai and M226 parasitemia is sub-patent, with very low mortality. H2O2 release peaked at 33,6 and 59 nM/2 x 106 cells for strains Y and F, respectively, 48 and 50 nM/2 x 106 for strains Costalimai and M226, 1t diferente days after infection. Histopathological findings of myositis, myocarditis, necrotizing artheritis and absence of macrophage parasitismo were found for strains F and Costalimai. Y strain infection presented moderate myocarditis and myositis, with parasites multiplying within macrophages.