Letter from Marcela Contreras, Director of the North London Blood Transfusion Centre, to Dr Harold H Gunson, National Director of the National Directorate of the Blood Transfusion Service re: factors to consider before placing orders for routine donor screening with the new anti-HCV test inc. whether ‘look back’ will be required, expense of obtaining and processing confirmatory samples, the data from the preliminary studies in Europe requiring extension and greater analysis