Counterflow centrifugation elutriation (CCE) has been widely used in research settings to separate mixed cell populations. With the advent of new increased-capacity equipment, elutriation technology has recently been adapted for clinical studies directed at prevention of graft-vs-host disease by depleting lymphocytes prior to bone marrow transplantation. The practical advantages of elutriation include (1) the large numbers of cells that can be processed in a single run, (2) high recovery and viability, (3) rapidity, and (4) reproducibility. The equipment, once modified, can be easily operated and maintained in a clinical laboratory setting. This article reviews the principles of CCE as they relate to the separation of blood and bone marrow cells and describes a recent clinical use for this instrumentation.