During the last 23 years, cord blood research has played important roles both in experimental and clinical hematology. Cord blood-derived hematopoietic stem and progenitor cells have been shown to possess particular biological features and their study has been very important in our understanding of hematopoietic development. Today, >20,000 umbilical cord blood (UCB) transplants have been performed worldwide and ∼460,000 UCB units are being stored in >47 UCB banks worldwide. Here a brief overview on some of the most relevant issues regarding cord blood research is presented. Copyright © 2011 IMSS. Published by Elsevier Inc. All rights reserved.