The study was a subproject within a Specialized Centers of Research (SCOR) in Transfusion Medicine. The experimental design was based on the study and analysis of several unique sets of data. One set consisted of abstracted patient data including ICD-9-CM diagnosis and procedure, DRG and red cell units transfused, from a constant set 100 of United States hospitals for the years 1980,82,84,86, to which a new set of data was added for the year 1989. A similar set of data were gathered from eight cooperating teaching hospitals over the first four years of the grant term; this set included data for transfusions of all blood components, autologous units and factor preparations. A third data base contained the data for four United States surveys conducted in 1982,84,86,87; and was expanded to include 1990 and 92. Using these data, four main tasks were addressed. A Pan-DRG red cell transfusion study was conducted to ascertain red cell use across all DRGs and ICD-9-CM codes. Extensive efforts were devoted to developing new methods to characterize transfusion practice. A series of studies were devoted to characterizing transfusions of all blood components in a selected number of ICD-9-CM classes. The purpose of the fourth task was to develop simpler and more rapid alternative methods for producing national estimates of transfusion activity; as part of this task,new surveys were conducted for 1990 and 92.