To improve the blood transfusion safety, according to the international recommendations anti-HCV negative blood donors are screened for HCV RNA. For decreasing the costs, the pools of 48 donor samples are tested. Until now 2,500,000 Polish donors were tested and HCV RNA was detected in 40. Anti-HCV was detected in plasma of all donors available for follow up for more than three months. No clinical symptoms were observed but in 20 donors slightly elevated ALT level was found. In the follow up, after detection of anti-HCV in 9/11 donors elevated ALT (167-2043 U/l) was observed. In two donors, out of 4 observed for more than 12 months HCV RNA was not detected in the follow up whereas anti-HCV were still present. In 7 donors probable source of infection was identified. The early detection of HCV infection is a serious challenge not only to transfusion medicine but also to general practitioners and hepatologists due to the necessity of further monitoring and treatment of infected individuals.