The selection of blood donors and the introduction of tests identifying virus-infected donors has led to a permanent increase in the safety of blood transfusion. In most European countries, there is a low risk of infection from viruses such as hepatitis B virus, hepatitis C virus and human immunodeficiency virus. Examples of viruses that pose a risk to children but not adults following transfusion-transmitted infection are parvovirus B19 and cytomegalovirus. Other viruses may be transmitted in the blood but, because of their low pathogenicity and high prevalence, they are not relevant for transfusion. Further work is required to determine the relevance of hepatitis A virus as a blood-borne viral infection. Human T-cell leukaemia virus is seldom transmitted during transfusion but may be an important risk factor in the future in some countries.