In industrialized countries, at a time when the viral safety of blood products has reached an all-time high, and when efforts to control public spending regularly prompt discussions about the cost-effectiveness of public health measures, a comprehensive review of the blood safety measures that have been implemented over the past four decades seems warranted. In this regard, the prevention of Human T-cell Lymphotropic Virus (HTLV) infection through transfusion—whose residual risk is currently estimated at 1 in 20 million donations in mainland France, excluding leukoreduction—appears to be a top priority in this debate. Indeed, its elimination from the transfusion chain relies on both universal antibody screening and the leukocyte removal of labile blood products, a process that could be sufficient on its own for this virus, which is exclusively found within leukocytes. To contribute to the debate, we have conducted estimates based on existing data. Currently, the probability that a leukoreduction error would affect an HTLV-positive donation has been estimated at 1 in 178 million. In the event that anti-HTLV antibody screening were discontinued in mainland France, the probability of a severe disease occurring following transfusion-transmitted HTLV would be 1 to 2 recipients per year in the absence of leukocyte removal, and one recipient every 192 years for a 10% failure rate in the filtration process. Despite a risk that appears to be fully under control, the only argument that could call screening into question would come from irrefutable proof of the safety of blood products—today thanks to leukoreduction and tomorrow through pathogen inactivation processes. (R.A.)