Blood transfusion affects outcomes after trauma, but whether elderly patients are disproportionately affected remains unknown. To determine the possible interaction between age, packed cell transfusion volume (PCTV), and mortality after injury, we designed a 6-year retrospective review (January 1995 through December 2000) of patients > or = 16 years of age who received blood transfusion within the first 24 hours after injury. One thousand three hundred twelve patients > or = 16 years of age admitted to our trauma center received packed red blood cells in the initial 24 hours after admission. Of the 1312 patients, 1028 (78%) were < or = 55 years and 284 (22%) were > 55 years of age, and overall mortality was 21.2 per cent. Age, Injury Severity Score (ISS) Glasbow Coma Scale (GCS), and PCTV emerged as independent predictors of mortality. PCTV for elderly survivors (4.6 units) was significantly less than that of younger survivors (6.7 units). Furthermore, mean PCTV for all survivors decreased progressively with advancing age. No patient >75 years with a PCTV > 12 units survived. Age and PCTV act independently, yet synergistically to increase mortality following injury.