Bone marrow transplantation (BMT) is limited by the paucity of HLA-matched donors and the frequent occurrence of graft-versus-host disease (GVHD). Recent clinical reports have implied that the use of umbilical cord blood (UCB) may alleviate some of the problems associated with BMT. Banks of frozen UCB could make the problem of finding suitable stem cell donors easier and stem cell grafts would be more readily available. However, definitive experiments are needed to develop optimal methods for collection, separation and storage of cryopreserved UCB for extended periods of time. We have found that several simple techniques may be utilized to collect large volumes of UCB (up to 220 ml). Also, modification of a common density gradient separation method permits recovery of large quantities of UCB mononuclear cells. Finally, we have examined the effects of prolonged frozen storage on the ability to recover viable and functional UCB, particularly stem/progenitor cells. It was observed that storage of UCB in liquid nitrogen for as long as 7 years had minimal effects on cell viability, cellular composition of UCB and progenitor/stem cell capacity. Thus, the establishment of UCB banks for use in transplantation appears to be a feasible approach.