A well-matched donor is important to the success of your transplant. You inherit half of your HLA markers from your mother and half from your father, so each brother and sister who has the same parents as you has a 25% chance of matching you. It is unlikely that extended family members will match you. Occasionally your parents and/or children may be tested to confirm your HLA typing and to make sure no possible donors are overlooked.
About 70% of people who need a transplant do not have a suitable donor in their family. If you do not have a donor in your family, your doctor can search the National Marrow Donor Program (NMDP) Registry for an unrelated donor or cord blood unit. The NMDP Registry lists more than 6 million volunteer donors and more than 60,000 cord blood units. Patients searching the NMDP Registry also have access to an additional 4 million donors through agreements with international cooperative registries.