The objective of this study is to promote the enrollment of healthy individuals to serve as kidney donors for patients undergoing research kidney transplantation at the NIH. Potential donors will be screened to make sure they are able to survive with a single kidney without significant medical risk. Additional tests will be taken to establish compatibility with the recipient. Compatible donors will be evaluated to determine which kidney is suitable for transplantation. Both the donation and transplantation procedure will be conducted on the same day. Appropriate post-operative care and follow-up will be provided at the Clinical Center.