The experience of 13 bone marrow processings is reported: 7 patients were affected by Acute Leukemias, 4 by Non Hodgkin's Lymphomas, 1 by Chronic Myelogenous Leukemia in complete remission after induction chemotherapy, 1 by Ewing's Sarcoma. Gravity sedimentation technique with 6% hydroxyethyl starch was used in all cases. A mean value of 0.754 x 10(8)/kg body weight mononuclear cells was harvested after sedimentation, with a mean recovery of 74.554%. Mean CFU-GM value was 0.543 x 10(4)/kg body weight. Only one evaluable patient, affected by ANLL, underwent Autologous Bone Marrow Transplantation and a full engraftment was noted on day +14. Results are discussed and further studies are proposed to clarify the relationship between the in vitro CFU-GM growth and the bone marrow engraftment.