Abstract A series of immunosuppressant mechanisms can manifest during surgical procedures, mediated by immune system cells or by humoral factors, to which the immunosuppressant effects of anesthesia or blood transfusion may be added, possibly further prejudicing the patient's immunological status, having important clinical repercussions such as increased incidence of postoperative infection or tumor reappearance. Autotransfusion of various types is an effective alternative to homologous transfusion as the former avoids immunodepressant effects. Preoperative autotransfusion [preoperative donation of autologous blood (PTAB)] has been shown to be one of the safest and most effective techniques and is the gold standard for autotransfusion. Problems of over collection, anemia and over transfusion that sometimes occur with PTAB can be solved with better screening procedures. Intraoperative autotransfusion (IAT) and postoperative autotransfusion (PAT) avoid such problems completely. However, IAT is only cost-effective in certain procedures (bleeding > 1,000-1,500 mL) and is not applicable in others, such as knee arthroplasty. PAT, on the other hand, in addition to being a good complement to other autotransfusion methods, may be the technique of choice in some procedures, such as knee arthroplasty, particularly if PTAB is contraindicated or if it is logistically difficult for a hospital to provide.However, in spite of its demonstrated efficacy, PAT of filtered blood has many critics, who warn of possible side effects and recommend the use of washed blood, which would make the procedure enormously more expensive unless it is performed with the same equipment used for IAT. Therefore, this review will analyze the hematologic characteristics of filtered blood, including metabolic status and survival of red blood cells, the components of the hemostatic system and inflammatory mediators, the content of fat particles and the possibility of their clearance, the incidence of infections and the dissemination of tumor cells. This analysis can reach the conclusion that salvaged filtered blood is a source of red blood cells of sufficient quality to be safely reinfused and that their reinfusion contributes significantly to reduce the need for homologous blood.