Background: From the data collected at the Ministry of Health from whole nation public and private blood banks (BB) find out the proportion of blood units discarded for being seropositive HBV, HCV, HIV, syphilis and Trypanosoma cruzi, and the seroprevalence of these infections among their donors. Methods: ELISA serological testing was done with 715, 393 donors seen at 535 blood banks between 2001 and 2002. Samples that were repeat reactive (RR) with the ELISA underwent supplementary Western blot (WB) testing. Results: Of the 715, 393 blood banks donors, 9,294 of them (1.3%) were positive for syphilis (VDRL), 6,107 (0.85%) for HBV (anti-HBc), 4,825 (0,67%) for T. cruzi, 3,859 (0.54%) for HCV and 1, 870 (0.26%) for HIV. In the Figure a summary of the seroprevalence of these infections, among public and private blood banks, per year, is presented. Conclusion: Although syphilis or Treponema pallidum infection was the most important blood-borne disease found in this study, the seroprevalence found is lower than others reported in other countries in the region (e.g. Goiânia, Brazil, 1989, 4.1%). For HBV and HCV, the seroprevalence estimates were also similar than those found in other countries in the region (such as Río de Janeiro, Brazil, where in 2005 the anti-HBc was 2.05% and 0.79% in 2004 for HCV), indicating high rates of infection by HBV and HCV and a persistent risk of HBV and HCV transmission by transfusion. For Chagas disease is also lower than others reported in other countries in the region (e.g. Goiânia, Brazil, 1989, 3.3%). Finally for HIV the found seroprevalence is similar to that reported in Mexico (Irapuato, Mexico, 2003,0.24%). But as seen herein, those seroprevalences are regional, and our report is nationwide. Further epidemiological research is expected.