Approximately half of cancer patients scheduled for major surgery are anemic. Also, a significant number of patients will present to the operating room with low platelet counts and coagulopathic disorders. Unfortunately, administration of red blood cells, platelets concentrates and fresh-frozen plasma is associated with unwanted adverse effects including fever, hemolytic reactions and transfusion-related immunomodulation (TRIM). TRIM is a multifactorial immunologic phenomenon in the recipient mediated by donor leukocytes, microparticles such as ectosomes, and growth factors. As some of these molecules are secreted in a time-dependent manner, blood storage time may play an important in TRIM, although the evidence is limited. Perioperative administration of red blood cells and associated TRIM has also been associated with increased recurrence of certain solid tumors, such as colorectal, lung, and hepatobiliary tumors. In this continuing education article, we review the available evidence on how perioperative blood product transfusions can affect oncological outcomes, such as cancer recurrence., (Copyright © 2014 Sociedad Española de Anestesiología, Reanimación y Terapéutica del Dolor. Publicado por Elsevier España, S.L.U. All rights reserved.)