Voluntary, free and regular donation are the first steps in reducing the risk of transmission infectious diseases transmitted by blood. Rigorous, screening and affirmative serological testing on a sensitive and highly specific tests of the latest generation of the market, improve the quality and safety of screening tests samples of blood donation. Percentage retest reactive serological samples for a period of 01. 10. 2013. 30. 09. 2014. in our Clinical Department approximate the value percentage retest reactive serologic samples in 2013 in Croatia, while the percentage of reactive confirmatory samples in our Clinical Department in the same period is significantly lower than the percentage of reactive confirmatory samples in Croatia in 2013. The percentage of reactive retest samples by molecular methods for HBV at the national level was twice higher compared to the percentage of our Clinical Institute while the percentage of HCV is equal. Presence of HIV at the level of our Clinical Department not exists and the national level the percentage of HIV is low. Infectious agents transmitted blood is a global public health problem. Also, the reasons are, with a large extent, the huge economic costs of treatment and a large number of complication. By separating reacitive, suspected or non-conforming donations, evaluated according to The evaluation process dose and blood donors according to the results of NAT and serological tests in transfusion activities of Croatia, the Institute for Clinical Transfusion Medicine Clinical Hospital Osijek, Department of serological and immunohaematological diagnostic blood donors, like all other regional centers and transfusion services improve and standardize procedures related to serological and molecular processing of collected blood donations. With introduction of molecular diagnostics and new highly specific method, reducing the WP, standardization work in the laboratory, with introduction of transfusion program e-Delphyn, automation and networking appliances with automatic transmission results testing, compliance with the principles of good laboratory practice and the proper application of blood and blood products reduced the risk of transmission of infectious agents transmitted with blood on recipients and raising the level of quality and safety of blood transfusion therapy.