BACKGROUND: A few recent studies have been conducted to analyzing the blood usage with regard to diagnosis of Korean recipients. We performed a study to analyze the usage of blood components. METHODS: Transfused components such as packed red blood cells (RBC), whole blood (WB), fresh frozen plasma (FFP), and platelet components (PLT) were estimated by the principal diagnoses of the patients, who were discharged from February 1998 to January 1999, according to the International Statistical Classification of Diseases (ICD)-10. RESULTS: Eleven percentage (2,227/20,650) of inpatients were transfused. The transfusion rate of hospitalized patients for RBCs, WBs, FFPs, and PLTs was 10.1%, 0.4%, 4.0% and 16.2 %, respectively. There was a difference in the sex ratio (1.6 male/female) in all blood components transfused. Of all investigated blood components (22,523 units), 10,729 units (47.6%) of RBCs, 240 units (1.1%) of WBs, 5,355 units (23.8%) of FFPs, and 6,199 units (27.5%) of PLTs were transfused. The hospitalized patients who received 1 unit of RBCs was 12.9%, and 2 units were most frequent transfused units (25.6%). Seventy-four percent of all 22,523 units were used in four diagnostic categories of highest blood usage; injury and poisoning (29.2%), nonhematologic neoplasms (16.3%), digestive system disease (16.1%) and circulatory system disease (12.5%). CONCLUSION: We performed usage analysis of blood components with regard to diagnosis, comparing the previous studies in other hospitals. This study could provide baseline transfusion information in relation to diagnosis, and help improve the quality control of blood utilization and transfusion practice.