AbstractBone marrow was collected from adult patients with various solid tumors who consented to participate in a study of myelo‐ablative chemotherapy followed by autologous bone marrow rescue. Twenty marrow suspensions were processed by using standard Procedure 3 (PRO‐3) for lymphocytapheresis without modification. A modified Procedure 1 (M‐PRO‐1) for plateletpheresis was employed for processing 34 marrow suspensions. For PRO‐3, mononuclear cell (MNC) recovery was 68 ± 22% of the starting marrow suspension (baseline), in a concentrate volume of 234 ± 53 ml. MNC represented 59 ± 27% of the total WBC count of the concentrate. The residual volume of RBC was 49 ± 47 ml. For M‐PRO‐1, MNC recovery was 63 ± 22% of the baseline in a concentrate volume of 200 ± 8 ml. MNC comprised 94 ± 7% of the total WBC count of the concentrate. RBC contamination was 7 ± 3 ml. Hematopoietic recovery, defined as the post‐transplant days when a sustained granulocyte count of 500/μL and a platelet count of 50,000/μL were achieved, was similar in the two groups and comparable to other reports utilizing otter methods and equipment for bone marrow concentration. Personnel time was significantly reduced compared to other procedures for bone marrow concentration due to increased automation.Although there was no significant difference in MNC recovery between the two groups (P > 0.5), M‐PRO‐1 was clearly superior to PRO‐3 because of the consistently high degree of purity of the MNC in the concentrate and minimal RBC contamination. M‐PRO‐1 is ideal in the setting of major ABO incompatible allogeneic marrow transplantation, marrow purging of malignant cells with 4‐HC, and in clinical situations where interim cryopreservation and storage of bone marrow are required.