Background: Reservation of blood leads to blood wastage if the blood is not transfused. Therefore, in some centers only blood type and screen are evaluated. In this study, the efficacy of a blood crossmatch-to-transfusion ratio was measured and then compared with the standard levels. Methods: This prospective study was conducted during one year in a university hospital. During this period, ۳۹۸ patients for whom blood had been requested were studied. In these patients, at the first surgical type, the laboratory tests (hematocrit, hemoglobin, platelet count, and prothrombin time) and the number of preoperative crossmatched and intraoperative transfused blood units were recorded. Then the crossmatch-to-transfusion ratio, transfusion probability, transfusion index, and correlation between related factors, and the transfusion ratio were evaluated. Results: In this cross-sectional study, blood was requested for ۳۹۸ patients. According to available blood unit deficiency, from ۹۶۱ blood unit requisitions, only ۴۵۶ units were crossmatched and ۱۲۳ units were transfused. The crossmatch-to-transfusion ratio, transfusion probability, and transfusion index were ۳.۷۱ (۷.۸۱ if all requisitions were crossmatched), ۱۶.۸۳%, and ۰.۳۱, respectively. The most unfavorable indexes were observed in patients who had ear, nose, and throat surgeries (۰ transfused from ۱۹ crossmatched blood units) and obstetric and gynecologic surgery (crossmatch-to-transfusion ratio was ۱۸.۶). The best indexes were related to thoracic surgery and neurosurgery (crossmatch-to-transfusion ratio was ۱.۵۳ and ۱.۵۴, respectively). There were no significant correlations between hemoglobin, hematocrit, platelet count, and prothrombin time with the number of transfused blood units (P = ۰.۲, ۰.۱۴, ۰.۲۶, and ۰.۰۶, respectively). Conclusion: The data for the crossmatch-to-transfusion ratio, transfusion probability, and transfusion index were suboptimal at this center, especially for ear, nose, and throat and obstetric and gynecologic surgeries. Further multidimensional studies and determination of a new model for blood requests and to decrease blood wastage are needed.