The efficacy of a program of transfusion of previously deposited autologous blood for patients undergoing total hip-replacement surgery was studied by comparing five different parameters for a group of fifty consecutive patients who deposited blood for autologous transfusion and a randomly chosen, closely matched control group of fifty patients who received only homologous blood. Sixty-two per cent of the patients in the group that deposited autologous blood did not receive additional homologous blood while in the hospital. The patients who deposited autologous blood had a mean preoperative hematocrit of 36 per cent, compared with 39 per cent for the control group, but the average postoperative hematocrits of the two groups did not differ (33 per cent). There was no significant difference in the average total loss of blood or need for replacement of blood between the groups. Transfusion-related complications developed in two patients in the control group. We concluded that previous deposit of autologous blood for transfusion is an effective method for reducing the need for transfusion of homologous blood and for avoiding the attendant complications of transfusion of homologous blood. This method of the replacement of blood should be considered for patients who are to undergo a major orthopaedic procedure on the hip.