The usual technique of harvesting bone marrow for allogeneic or autologous transplantation involves passage of the marrow suspension through discs of stainless steel mesh of increasingly small diameter. We describe a sterile technique which is much less messy and produces a single cell suspension. Potter-Elvehjem homogenizers are used to break up the marrow particles. This procedure has been used successfully in 6 patients where allogeneic transplantation was performed and in 6 harvests of autologous marrow. Marrow cryopreserved in this way contains viable committed stem cells and is not subject to agglutination following subsequent thawing.