Although first used only to treat children - due to the low cell dose infused - umbilical cord blood (UCB) has been proven effective in treating adults when cord blood units of sufficient cell dose and HLA match are used. In this review article, the authors highlight the improving results in UCB transplantation in adults, and discuss the use of double UCB units, improved supportive care techniques, and ongoing efforts to expand UCB cells to reduce the time to stem cell engraftment.