We report the long-term evaluation over 12 years of a simplified technique for stem-cell cryopreservation at -80 degrees C without rate-controlled freezing and with 5% (n=251) or 10% (n=47) DMSO as the sole cryoprotectant. Platelet recovery was greater in the 5% DMSO group while long-term hematological recovery did not differ. Factors influencing a faster hematological recovery were infusion of more than 2.7x10(6)/Kg of CD34+ cells, 10% DMSO cryopreservation and G-CSF. We confirm that the procedure is feasible with reduction in infusion-related toxicity from 60% using 5% DMSO. Differences in hematological reconstitution were not clinically significant if a minimum of 1.5x10(6)/Kg CD34+-cells were infused.