Background: The biotherapies are drugs widely utilized against infectious diseases. Biotherapies’ profylatic and therapeutic action against Chagas Disease is currently being investigated, but it is needed to develop further controlled experiments “in vivoâ€ÂÂ, which could define more clearly: dilution, dose, time of use and, if possible, the action mechanisms of these ultradiluted medicaments [1,2].
 
 Aim: Evaluate the effect biotherapies T. cruzi 15x, 16x, 17x and “potency chordsâ€ÂÂ, on experimental infection by T. cruzi.
 
 Methodology: A blind, controlled and randomized by drawing test was performed. Animals: 29 male Swiss mice, four weeks old were utilized. The animals were kept at Parasitology Vivarium/State University of Maringá (UEM), in ideal conditions of temperature (22±2)ºC and photoperiod (light / dark cycle 12h). Mice have been inoculated intraperitoneally with 1400 blood trypomastigotes Y strain and divided in groups: IC – Infection control (treated with distilled water – 9 animals); TBBA15x3days – Treated with biotherapy 15x 3 days before and 3 days after infection (5 animals); TBBA16x3days – Treated with biotherapy 16x 3 days before and 3 days after infection (5 animals); TBBA17x3days – Treated with biotherapy 17x 3 days before and 3 days after infection (5 animals); TBBAChords3days – Treated with biotherapy 15x, 16x, 17x “potency chordsâ€ÂÂ, 3 days before and 3 days after infection (5 animals). Biotherapies: prepared by a homeopathic pharmacist from UEM, according to Farmacopéia Homeopática Brasileira [3]. Biotherapies treatment schedule: diluted in distilled water (10µL/mL in ambar bottles – renewed each two days) offered ad libitum, 3 days before and 3 days after infection in all groups. Parasitological parameters: parasitemia was assessed from infection until death, according to Brener’s technique [4] with 5µL of blood collected from the tail vein and examined in optical microscope. Pre-patent period, patent period, total parasitemia, survival and morbidity were obtained from the parasitemia curve. Clinical parameters: Visually assessed (presence or absence): body hair aspect (bristling), edema, movement and diarrhea. Measured: body weight, temperature, food and water intake. Ethics: This study has been approved by the UEM Ethics Committee for Experiments in Animals - Registration 030/2008. Statistical analysis: was performed using the tests Kruskal Wallis and Mann-Whitney tests, significance of 5%.
 
 Results: There was not statistical difference between total parasitemia of the groups treated with biotherapies and the IC group (p=0.6819). The parasitemia curve of group TBBAChords3days was greater then the IC (p=0.0418). Despite this increase, patent period and mortality both showed a decreasing tendency, while pre patent period and survival time increased (p=0.373). The same tendency results were observed for TBBA17x3days results (Table 1). Survival of at least one mice in groups TBBA17x3days and TBBAChords3days is worthy of discussion, since Y strain causes 100% mortality in these experimental conditions.
 
 Groups TBBA17x3days and TBBAChords3days showed better evolution than IC group for body weight, temperature, food and water intake (p=0.05), body hair aspect and edema developing. Diarrhea and hind legs paralysis were only observed in mice belonging to groups IC and TBAA16x3days.
 
 Conclusions: Superior effect was obtained with biotherapies 17x and “Potency Chordsâ€ÂÂ, both for clinical and parasitological parameters. “Potency chords†has proper effect which distinguishes it from the individual effects of the dilutions that compound it.