BACKGROUND: Collections, processing, and transfusions of blood and blood components in the US in 1997 were measured and compared with 1994 and prior years. STUDY DESIGN AND METHODS: Questionnaires were returned by 2391 blood centers, AABB member hospitals, nonmember hospitals, and other facilities. Statistical procedures were used to verify that the sample was representative and to estimate national collections and utilization. RESULTS: The gross domestic blood supply in the US in 1997 was 12,602,000 units, 5.5 percent less than in 1994. It included 11,741,000 units of allogeneic community blood, 643,000 units of autologous blood, and 205,000 units of allogeneic-directed blood. Platelet transfusions amounted to 9,037,000 platelet concentrate equivalent units, of which 62.4 percent were apheresis packs. Compared with 1994, total platelet units transfused increased by 14.9 percent and single-donor platelet units transfused increased by 31.7 percent, whereas platelet concentrate transfusion declined by 3.8 percent. Transfusions of FFP increased by 26.6 percent compared with 1994. CONCLUSIONS: The margin of US allogeneic blood supply in excess of allogeneic transfusions in 1997 was 630,000 units, 5.4 percent of total allogeneic supply as compared with margins in prior years ranging between 9.3 and 10.9 percent. Although overall allogeneic available supply in 1994 was adequate to meet transfusion demand, the decrease in the margin between 1994 and 1997 is cause for concern. The rate of whole-blood collections in 1997 per 1000 members of the population aged 18 to 65 years was 12.6 percent lower than 1994. The RBC transfusion rate per 1000 members of the population in 1997 remained nearly the same as in 1994. However, the rates of platelet and of plasma transfusions both increased.