Among the well known transfusion-associated risks, the transmission of pathogenic viruses is regarded as one of the most serious. Over the past two decades, a series of overlapping safety procedures have been successively implemented to minimise this risk. It is now generally considered that the risk of transmitting viral infections via blood products is very low in developed countries. The present study analyses the incidence of the key infectious diseases HIV, hepatitis B virus (HBV) and hepatitis C virus (HCV) between 1996 and 2003 from 99% of voluntary repeat blood donors visiting the blood transfusion service of the Swiss Red Cross. Furthermore the estimated risk of these viral markers was calculated. From 1996 to 2003 the incidence rate for HCV decreased continuously, whereas no significant decrease in the incidence rate of HIV and HBV was observed. From 2001 to 2003, the last calculated period, the residual risk was estimated to be 1 in 1,900,000 for HIV, 1 in 2,200,0000 for HCV and 1 in 115,000 for HBV, respectively. This agrees with international studies, which have been shown that the estimated residual risk for HBV between 1996 and 2003 is higher than that of HCV and HIV.