Infusion of thawed cryopreserved autologous stem cells (SC) is associated with a variety of complications due to the presence of dimethyl sulfoxide (DMSO) and free hemoglobin and to volume overload. Commonly, the DMSO is not removed before infusion for fear that prolonged in vitro exposure of the cells to DMSO leads to loss of clonogenic activity. We describe a simple technique for the substantial reduction in volume and DMSO content of bone marrow (BM) and peripheral blood stem cell (PBSC) suspensions. Sixty-five patients were transplanted with thawed, volume-reduced SC cryopreserved according to Stiff et al. Semiautomated volume reduction was performed on a COBE 2991 cell processor. The median volumes of cryopreserved SC were 1152 ml and 933 ml for the pools of PBSC products and the mixed pools of BM and PBSC, respectively, whereas the volume of SC infused was 153 ml (78% reduction). There were no differences in cell recoveries between PBSC and BM (98%). Only 2 patients demonstrated minimal side effects during infusion. A cohort of 16 metastatic breast cancer patients underwent PBSC harvests following chemotherapy/G-CSF priming and subsequent autotransplantation. Median time to an absolute neutrophil count > 500/microliters was 8 days (range 6-14 days), and median time to a platelet count > 20,000/microliters was 11 days (range 6-18 days). Volume reduction of SC products without the risk of graft failure was performed simply and resulted in few complications during infusion.