BACKGROUND: There are few recent studies on transfusion practice and blood use with regard to diagnoses of Korean recipients. We conducted a survey of blood component use in Yonsei University Medical Center in Seoul, Korea. METHODS: A survey was carried out on blood component transfusion from January 2000 to June 2000. Transfused components were listed by broad diagnostic categories formed from the principal diagnoses of the recipients according to the ICD-10. RESULTS: Of all investigated components (67,433 units), 18,623 units of RBCs (27.6%), 10,203 units of FFP (15.1%), 38,547 units of platelets (57.2%), and 60 units of whole blood (0.1%) were transfused. The transfusion rate in relation to sex was 1.7:1 and the majority of all blood units were transfused to patients aged <65 yrs (85.9%). The rate of blood component transfusion was the highest in the department of internal medicine (47,451 units, 70.4%). Of 18,623 RBCs units and 10,203 FFP units, 70.8% and 74.5% were transfused to patients in four diagnostic categories; neoplasms, digestive system diseases, circulatory system diseases, and leukemia or lymphoma. Of 38,547 platelets units, 87.8% were used in patients with neoplasms, leukemia or lymphoma, digestive system diseases and diseases of the blood and blood-forming organs. CONCLUSIONS: This survey provides information on the blood component usage in tertiary-care teaching hospital in Seoul, Korea. It demonstrates the concentration of today's blood utilization among a few diagnostic categories. This information is relevant for quality management of transfusion practice, cost analyses and for planning local and regional blood donation programs.