In this chapter it is emphasized the importance to guarantee safety and high quality blood transfusions. Besides, the following topics are analyzed: the importance of Trypanoson7a cruZi infection acquired by blood transfusions, the obligatory screening implemented in Chilean blood banks and serological diagnostic techniques used that for, the seroprevalence observed, the importance to confirm results and methods recommended in this purpose and, to notify the donor once the infection is confirmed. In addition a facsimil of a letter used to notify the positive donor is included as guidelines to make advice after, attaching a proforma of clinical-epidemiological registration to refer the donor to medical evaluation and treatment.