Objective - To evaluate the effects of different forms of administration of the blood trypomastigotes biotherapy 7dH in mice experimentally infected with Trypanosoma cruzi.Material and methods - Male swiss mice were inoculated with 1400 blood trypomastigotes of the Y strain of T. cruzi and allocated into 5 treatment groups: IC (distilled water); TCBZ (benznidazole); TBA7dH (biotherapy 7dH 20 days after infection); TBB7dH7 (biotherapy 7dH seven days before infection); TBB7dH30 (biotherapy 7dH 30 days before infection). Parasitological parameters assessed included pre-patent and patent periods, parasitemia peak, total parasitemia, mortality and survival rates. Cure index was obtained by fresh blood examination, hemoculture and polymerase chain reaction (PCR).Results - The TBB7dH7 group showed a reduction in parasitemia peak, parasitemia area under the curve and total parasitemia. TBB7dH30 showed a tendency to increased pre-patent and survival periods, peak parasitemia was increased without increased total parasitemia. TBA7dH did not present significant alterations in the parasitological parameters analyzed.Conclusions - Biotherapy 7dH given before infection (7 or 30 days) produces different effects suggesting modulation of the host’s immune system. The effects range from reduced parasitemia to its effective increase. The use of biotherapy to treat T. cruzi infection including dose, potency and schedule deserves further investigation.