Of 182 consecutive patients undergoing allogeneic bone marrow transplantation (BMT), the relative numbers of those who received red blood cells (RBC), platelets (PLT), and granulocytes were 82%, 96%, and 26%, respectively. The transfused patients received an average of 1.26 (SD +/- 2.0) RBC units, 9.41 (SD +/- 13.2) PLT transfusions, and 0.33 (SD +/- 1.1) granulocyte concentrates per week per 50 kg body wt. in the period starting on the day of bone marrow transplantation (BMT) up to 60 days post BMT. The total number of units per transfused patient was 7.7 (range 1-63) RBC, 55.2 (range 2-394) PLT and 6.2 (range 1-36) granulocytes in the same period. Patients with grades II-IV acute graft-versus-host disease (GVHD) needed more RBC and PLT (p less than 0.001) than patients with grades 0-I acute GVHD. Patients with late engraftment required more granulocyte and PLT transfusion than those with early engraftment (p less than 0.05). Patients with high-risk malignancy had greater need for RBC and PLT than "low-risk patients" (p less than 0.02 and p less than 0.01), respectively). Patients with major ABO-incompatible donors showed a greater need for RBC than patients with minor ABO incompatibility (p = 0.02) or ABO identical donors (p = 0.01). Patients with relatively poor estimated survival required the most RBC and PLT.