One hundred and sixty-six patients with malignancies had 170 consecutive bone marrow collection procedures in anticipation of autologous transplantation. The morbidity associated with these harvest procedures was increased compared to morbidity experienced by normal donors who had marrow collected for allogeneic transplantation when unexplained fever (p = 0.02) and infection (p = 0.008) were considered. No differences could be found in the characteristics of the harvested marrow including concentration of nucleated cells and nucleated cell content between the two donor groups. No deaths occurred as a result of the harvest procedure. However, a previously reported series of autologous marrow donors from a different institution did not demonstrate an increased morbidity associated with marrow harvesting when compared to the same series of normal donors. The differences found in the two autologous series might be explained by differing characteristics of the patient populations. The increased morbidity found in our patients was tolerable and reversible and not a contraindication to high-dose therapy with autologous bone marrow transplantation.