Homologous blood transfusions are not without risks, especially in young women and girls. In patients undergoing certain elective surgical procedures autologous blood transfusion is a good alternative. Normovolaemic haemodilution in association with autotransfusion offers the additional advantages of reduced loss of red cell mass during the operation and an increase in tissue blood flow. In this study twenty-seven adolescent patients undergoing Harrington instrumentation for idiopathic scoliosis had haemodilutional autotransfusions during their operations, none requiring homologous blood. Eighteen were given an average of 750 millilitres of homologous blood in the postoperative period which compared favourably with controls who required 1280 millilitres.