Umbilical cord blood transplantation (UCBT) is an expanding practice for both pediatric and adult patients. Rapid availability, low risk of infectious disease transmission, lower risk of graft-versus-host disease, and lack of risk for the donor makes UCB an attractive alternative source of hematopoietic stem cells for transplantation. We review the state of the art of pediatric and adult UCBT and important aspects of UCB banking. Current strategies to improve clinical results and expand access to UCBT to a larger number of adult patients are discussed. New approaches to enhance hematopoietic recovery by the use of accessory cells or direct intra-bone marrow injection are also reviewed.