We describe an operating theater blood transaction system (OTBTS) that is a novel computer software system incorporating electronic crossmatch and the concept of a “self-service” blood banking system in the operating theater. Through this system, the surgeons and the anesthetists can issue blood units for intraoperative transfusion for the patients with a negative antibody screen without the need for a porter service or pneumatic tube system. Since implementation of the OTBTS, the time for obtaining compatible blood for intraoperative transfusion has been reduced from 20 to 30 minutes to around 1 minute. Furthermore, the crossmatch-transfusion ratio was reduced to 1.05. The 23% of patients who required extra blood units (ie, more than originally anticipated) during surgery further benefited from the system. The blood stock reserved for patients undergoing surgery was reduced by 20%. Therefore, the OTBTS is a system that can greatly enhance the efficiency and safety of intraoperative transfusion and can also save workforce resources.