Objectives -To review the principles and available technology for pretransfusion testing in veterinary medicine and discuss the indications and importance of test performance before RBC transfusion. Data Sources -Current human and veterinary medical literature: original research articles and scientific reviews. Summary -Indications for RBC transfusion in veterinary medicine include severe anemia or tissue hypoxia resulting from blood loss, decreased erythrocyte production, and hemolyzing conditions such as immunemediated anemia and neonatal isoerythrolysis. Proper blood sample collection, handling, and identification are imperative for high-quality pretransfusion testing. Point-of-care blood typing methods including both typing cards and rapid gel agglutination are readily available for some species. Following blood typing, crossmatching is performed on one or more donor units of appropriate blood type. As an alternative to technically demanding tube crossmatching methods, a point-of-care gel agglutination method has recently become available for use in dogs and cats. Crossmatching reduces the risk of hemolytic transfusion reactions but does not completely eliminate the risk of other types of transfusion reactions in veterinary patients, and for this reason, all transfusion reactions should be appropriately documented and investigated. Conclusion -The administration of blood products is a resource-intensive function of veterinary medicine and optimizing patient safety in transfusion medicine is multifaceted. Adverse reactions can be life threatening. Appropriate donor screening and collection combined with pretransfusion testing decreases the occurrence of incompatible transfusion reactions.