Several automated procedures are now available to enrich stem cells from large bone marrow (BM) volumes prior to ex vivo treatment or cryopreservation. This report details our experience using a ficoll-hypaque (F/H) gradient on Cobe 2991 cell washer and a CS 3000 continuous flow separator, on 90 BM processed for allogeneic and autologous transplantation. In the Cobe series, from 70 BM aspirates, 89 +/- 5% of the original mononuclear cells (MNC) was found in the light density fraction with a erythrocytes (RBC) and granulocytes (PMN) removal of 98 +/- 1 and 97 +/- 4.5%, respectively. Over 80% of the initial myeloid precursors (CFU-GM) were recovered in a small final volume. Twenty BM processing were performed with a CS 3000 separator using program "3" and granulo chamber. This technique yielded 86 +/- 9% of the initial MNC while 85 +/- 10% of RBC and 90 +/- 1.1% of PMN was removed. Over 75% of the original CFU-GM was recovered in the final product. Both techniques are effective to large-scale purification of progenitor cells and readily available as routine procedures for marrow processing.