Since the first successful transplantation of umbilical cord blood in 1988, cord blood has become an important source of hematopoietic stem and progenitor cells for the treatment of blood and genetic disorders. Significant progress has been accompanied by challenges for scientists, ethicists, and health policy makers. With the recent recognition of the need for a national system for the collection, banking, distribution, and use of cord blood and the increasing focus on cord blood as an alternative to embryos as a source of tissue for regenerative medicine, cord blood has garnered significant attention. We review the development of cord blood banking and transplantation and then discuss the scientific and ethical issues influencing both established and investigational practices surrounding cord blood collection, banking, and use.